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Kubeadm

Kubeadm is a tool built to provide kubeadm init and kubeadm join as best-practice "fast paths" for creating Kubernetes clusters.

kubeadm performs the actions necessary to get a minimum viable cluster up and running. By design, it cares only about bootstrapping, not about provisioning machines. Likewise, installing various nice-to-have addons, like the Kubernetes Dashboard, monitoring solutions, and cloud-specific addons, is not in scope.

Instead, we expect higher-level and more tailored tooling to be built on top of kubeadm, and ideally, using kubeadm as the basis of all deployments will make it easier to create conformant clusters.

How to install

To install kubeadm, see the installation guide.

What's next

  • kubeadm init to bootstrap a Kubernetes control-plane node
  • kubeadm join to bootstrap a Kubernetes worker node and join it to the cluster
  • kubeadm upgrade to upgrade a Kubernetes cluster to a newer version
  • kubeadm config if you initialized your cluster using kubeadm v1.7.x or lower, to configure your cluster for kubeadm upgrade
  • kubeadm token to manage tokens for kubeadm join
  • kubeadm reset to revert any changes made to this host by kubeadm init or kubeadm join
  • kubeadm certs to manage Kubernetes certificates
  • kubeadm kubeconfig to manage kubeconfig files
  • kubeadm version to print the kubeadm version
  • kubeadm alpha to preview a set of features made available for gathering feedback from the community

1 - Kubeadm Generated

1.1 -

kubeadm: easily bootstrap a secure Kubernetes cluster

Synopsis

┌──────────────────────────────────────────────────────────┐
│ KUBEADM                                                  │
│ Easily bootstrap a secure Kubernetes cluster             │
│                                                          │
│ Please give us feedback at:                              │
│ https://github.com/kubernetes/kubeadm/issues             │
└──────────────────────────────────────────────────────────┘

Example usage:

Create a two-machine cluster with one control-plane node
(which controls the cluster), and one worker node
(where your workloads, like Pods and Deployments run).

┌──────────────────────────────────────────────────────────┐
│ On the first machine:                                    │
├──────────────────────────────────────────────────────────┤
│ control-plane# kubeadm init                              │
└──────────────────────────────────────────────────────────┘

┌──────────────────────────────────────────────────────────┐
│ On the second machine:                                   │
├──────────────────────────────────────────────────────────┤
│ worker# kubeadm join <arguments-returned-from-init>      │
└──────────────────────────────────────────────────────────┘

You can then repeat the second step on as many other machines as you like.

Options

-h, --help

help for kubeadm

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.2 -

Kubeadm experimental sub-commands

Synopsis

Kubeadm experimental sub-commands

Options

-h, --help

help for alpha

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.3 -

Kubeconfig file utilities

Synopsis

Kubeconfig file utilities.

Alpha Disclaimer: this command is currently alpha.

Options

-h, --help

help for kubeconfig

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.4 -

Output a kubeconfig file for an additional user

Synopsis

Output a kubeconfig file for an additional user.

Alpha Disclaimer: this command is currently alpha.

kubeadm alpha kubeconfig user [flags]

Examples

  # Output a kubeconfig file for an additional user named foo using a kubeadm config file bar
  kubeadm alpha kubeconfig user --client-name=foo --config=bar

Options

--client-name string

The name of user. It will be used as the CN if client certificates are created

--config string

Path to a kubeadm configuration file.

-h, --help

help for user

--org strings

The orgnizations of the client certificate. It will be used as the O if client certificates are created

--token string

The token that should be used as the authentication mechanism for this kubeconfig, instead of client certificates

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.5 -

Commands related to handling kubernetes certificates

Synopsis

Commands related to handling kubernetes certificates

Options

-h, --help

help for certs

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.6 -

Generate certificate keys

Synopsis

This command will print out a secure randomly-generated certificate key that can be used with the "init" command.

You can also use "kubeadm init --upload-certs" without specifying a certificate key and it will generate and print one for you.

kubeadm certs certificate-key [flags]

Options

-h, --help

help for certificate-key

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.7 -

Check certificates expiration for a Kubernetes cluster

Synopsis

Checks expiration for the certificates in the local PKI managed by kubeadm.

kubeadm certs check-expiration [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

-h, --help

help for check-expiration

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.8 -

Generate keys and certificate signing requests

Synopsis

Generates keys and certificate signing requests (CSRs) for all the certificates required to run the control plane. This command also generates partial kubeconfig files with private key data in the "users > user > client-key-data" field, and for each kubeconfig file an accompanying ".csr" file is created.

This command is designed for use in Kubeadm External CA Mode. It generates CSRs which you can then submit to your external certificate authority for signing.

The PEM encoded signed certificates should then be saved alongside the key files, using ".crt" as the file extension, or in the case of kubeconfig files, the PEM encoded signed certificate should be base64 encoded and added to the kubeconfig file in the "users > user > client-certificate-data" field.

kubeadm certs generate-csr [flags]

Examples

  # The following command will generate keys and CSRs for all control-plane certificates and kubeconfig files:
  kubeadm alpha certs generate-csr --kubeconfig-dir /tmp/etc-k8s --cert-dir /tmp/etc-k8s/pki

Options

--cert-dir string

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

-h, --help

help for generate-csr

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.9 -

Renew certificates for a Kubernetes cluster

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm certs renew [flags]

Options

-h, --help

help for renew

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.10 -

Renew the certificate embedded in the kubeconfig file for the admin to use and for kubeadm itself

Synopsis

Renew the certificate embedded in the kubeconfig file for the admin to use and for kubeadm itself.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew admin.conf [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for admin.conf

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.11 -

Renew all available certificates

Synopsis

Renew all known certificates necessary to run the control plane. Renewals are run unconditionally, regardless of expiration date. Renewals can also be run individually for more control.

kubeadm certs renew all [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for all

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.12 -

Renew the certificate the apiserver uses to access etcd

Synopsis

Renew the certificate the apiserver uses to access etcd.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew apiserver-etcd-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for apiserver-etcd-client

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.13 -

Renew the certificate for the API server to connect to kubelet

Synopsis

Renew the certificate for the API server to connect to kubelet.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew apiserver-kubelet-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for apiserver-kubelet-client

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.14 -

Renew the certificate for serving the Kubernetes API

Synopsis

Renew the certificate for serving the Kubernetes API.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew apiserver [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for apiserver

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.15 -

Renew the certificate embedded in the kubeconfig file for the controller manager to use

Synopsis

Renew the certificate embedded in the kubeconfig file for the controller manager to use.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew controller-manager.conf [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for controller-manager.conf

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.16 -

Renew the certificate for liveness probes to healthcheck etcd

Synopsis

Renew the certificate for liveness probes to healthcheck etcd.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew etcd-healthcheck-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for etcd-healthcheck-client

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.17 -

Renew the certificate for etcd nodes to communicate with each other

Synopsis

Renew the certificate for etcd nodes to communicate with each other.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew etcd-peer [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for etcd-peer

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.18 -

Renew the certificate for serving etcd

Synopsis

Renew the certificate for serving etcd.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew etcd-server [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for etcd-server

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.19 -

Renew the certificate for the front proxy client

Synopsis

Renew the certificate for the front proxy client.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew front-proxy-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for front-proxy-client

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.20 -

Renew the certificate embedded in the kubeconfig file for the scheduler manager to use

Synopsis

Renew the certificate embedded in the kubeconfig file for the scheduler manager to use.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew scheduler.conf [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for scheduler.conf

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.21 -

Output shell completion code for the specified shell (bash or zsh)

Synopsis

Output shell completion code for the specified shell (bash or zsh). The shell code must be evaluated to provide interactive completion of kubeadm commands. This can be done by sourcing it from the .bash_profile.

Note: this requires the bash-completion framework.

To install it on Mac use homebrew: $ brew install bash-completion Once installed, bash_completion must be evaluated. This can be done by adding the following line to the .bash_profile $ source $(brew --prefix)/etc/bash_completion

If bash-completion is not installed on Linux, please install the 'bash-completion' package via your distribution's package manager.

Note for zsh users: [1] zsh completions are only supported in versions of zsh >= 5.2

kubeadm completion SHELL [flags]

Examples


# Install bash completion on a Mac using homebrew
brew install bash-completion
printf "\n# Bash completion support\nsource $(brew --prefix)/etc/bash_completion\n" >> $HOME/.bash_profile
source $HOME/.bash_profile

# Load the kubeadm completion code for bash into the current shell
source <(kubeadm completion bash)

# Write bash completion code to a file and source it from .bash_profile
kubeadm completion bash > ~/.kube/kubeadm_completion.bash.inc
printf "\n# Kubeadm shell completion\nsource '$HOME/.kube/kubeadm_completion.bash.inc'\n" >> $HOME/.bash_profile
source $HOME/.bash_profile

# Load the kubeadm completion code for zsh[1] into the current shell
source <(kubeadm completion zsh)

Options

-h, --help

help for completion

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.22 -

Manage configuration for a kubeadm cluster persisted in a ConfigMap in the cluster

Synopsis

There is a ConfigMap in the kube-system namespace called "kubeadm-config" that kubeadm uses to store internal configuration about the cluster. kubeadm CLI v1.8.0+ automatically creates this ConfigMap with the config used with 'kubeadm init', but if you initialized your cluster using kubeadm v1.7.x or lower, you must use the 'config upload' command to create this ConfigMap. This is required so that 'kubeadm upgrade' can configure your upgraded cluster correctly.

kubeadm config [flags]

Options

-h, --help

help for config

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.23 -

Interact with container images used by kubeadm

Synopsis

Interact with container images used by kubeadm

kubeadm config images [flags]

Options

-h, --help

help for images

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.24 -

Print a list of images kubeadm will use. The configuration file is used in case any images or image repositories are customized

Synopsis

Print a list of images kubeadm will use. The configuration file is used in case any images or image repositories are customized

kubeadm config images list [flags]

Options

--allow-missing-template-keys     Default: true

If true, ignore any errors in templates when a field or map key is missing in the template. Only applies to golang and jsonpath output formats.

--config string

Path to a kubeadm configuration file.

-o, --experimental-output string     Default: "text"

Output format. One of: text|json|yaml|go-template|go-template-file|template|templatefile|jsonpath|jsonpath-as-json|jsonpath-file.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for list

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--show-managed-fields

If true, keep the managedFields when printing objects in JSON or YAML format.

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.25 -

Pull images used by kubeadm

Synopsis

Pull images used by kubeadm

kubeadm config images pull [flags]

Options

--config string

Path to a kubeadm configuration file.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for pull

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.26 -

Read an older version of the kubeadm configuration API types from a file, and output the similar config object for the newer version

Synopsis

This command lets you convert configuration objects of older versions to the latest supported version, locally in the CLI tool without ever touching anything in the cluster. In this version of kubeadm, the following API versions are supported:

  • kubeadm.k8s.io/v1beta2

Further, kubeadm can only write out config of version "kubeadm.k8s.io/v1beta2", but read both types. So regardless of what version you pass to the --old-config parameter here, the API object will be read, deserialized, defaulted, converted, validated, and re-serialized when written to stdout or --new-config if specified.

In other words, the output of this command is what kubeadm actually would read internally if you submitted this file to "kubeadm init"

kubeadm config migrate [flags]

Options

-h, --help

help for migrate

--new-config string

Path to the resulting equivalent kubeadm config file using the new API version. Optional, if not specified output will be sent to STDOUT.

--old-config string

Path to the kubeadm config file that is using an old API version and should be converted. This flag is mandatory.

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.27 -

Print configuration

Synopsis

This command prints configurations for subcommands provided. For details, see: https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2

kubeadm config print [flags]

Options

-h, --help

help for print

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.28 -

Print default init configuration, that can be used for 'kubeadm init'

Synopsis

This command prints objects such as the default init configuration that is used for 'kubeadm init'.

Note that sensitive values like the Bootstrap Token fields are replaced with placeholder values like "abcdef.0123456789abcdef" in order to pass validation but not perform the real computation for creating a token.

kubeadm config print init-defaults [flags]

Options

--component-configs strings

A comma-separated list for component config API objects to print the default values for. Available values: [KubeProxyConfiguration KubeletConfiguration]. If this flag is not set, no component configs will be printed.

-h, --help

help for init-defaults

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.29 -

Print default join configuration, that can be used for 'kubeadm join'

Synopsis

This command prints objects such as the default join configuration that is used for 'kubeadm join'.

Note that sensitive values like the Bootstrap Token fields are replaced with placeholder values like "abcdef.0123456789abcdef" in order to pass validation but not perform the real computation for creating a token.

kubeadm config print join-defaults [flags]

Options

--component-configs strings

A comma-separated list for component config API objects to print the default values for. Available values: [KubeProxyConfiguration KubeletConfiguration]. If this flag is not set, no component configs will be printed.

-h, --help

help for join-defaults

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.30 -

Run this command in order to set up the Kubernetes control plane

Synopsis

Run this command in order to set up the Kubernetes control plane

The "init" command executes the following phases:

preflight                    Run pre-flight checks
certs                        Certificate generation
  /ca                          Generate the self-signed Kubernetes CA to provision identities for other Kubernetes components
  /apiserver                   Generate the certificate for serving the Kubernetes API
  /apiserver-kubelet-client    Generate the certificate for the API server to connect to kubelet
  /front-proxy-ca              Generate the self-signed CA to provision identities for front proxy
  /front-proxy-client          Generate the certificate for the front proxy client
  /etcd-ca                     Generate the self-signed CA to provision identities for etcd
  /etcd-server                 Generate the certificate for serving etcd
  /etcd-peer                   Generate the certificate for etcd nodes to communicate with each other
  /etcd-healthcheck-client     Generate the certificate for liveness probes to healthcheck etcd
  /apiserver-etcd-client       Generate the certificate the apiserver uses to access etcd
  /sa                          Generate a private key for signing service account tokens along with its public key
kubeconfig                   Generate all kubeconfig files necessary to establish the control plane and the admin kubeconfig file
  /admin                       Generate a kubeconfig file for the admin to use and for kubeadm itself
  /kubelet                     Generate a kubeconfig file for the kubelet to use *only* for cluster bootstrapping purposes
  /controller-manager          Generate a kubeconfig file for the controller manager to use
  /scheduler                   Generate a kubeconfig file for the scheduler to use
kubelet-start                Write kubelet settings and (re)start the kubelet
control-plane                Generate all static Pod manifest files necessary to establish the control plane
  /apiserver                   Generates the kube-apiserver static Pod manifest
  /controller-manager          Generates the kube-controller-manager static Pod manifest
  /scheduler                   Generates the kube-scheduler static Pod manifest
etcd                         Generate static Pod manifest file for local etcd
  /local                       Generate the static Pod manifest file for a local, single-node local etcd instance
upload-config                Upload the kubeadm and kubelet configuration to a ConfigMap
  /kubeadm                     Upload the kubeadm ClusterConfiguration to a ConfigMap
  /kubelet                     Upload the kubelet component config to a ConfigMap
upload-certs                 Upload certificates to kubeadm-certs
mark-control-plane           Mark a node as a control-plane
bootstrap-token              Generates bootstrap tokens used to join a node to a cluster
kubelet-finalize             Updates settings relevant to the kubelet after TLS bootstrap
  /experimental-cert-rotation  Enable kubelet client certificate rotation
addon                        Install required addons for passing conformance tests
  /coredns                     Install the CoreDNS addon to a Kubernetes cluster
  /kube-proxy                  Install the kube-proxy addon to a Kubernetes cluster
kubeadm init [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--apiserver-cert-extra-sans strings

Optional extra Subject Alternative Names (SANs) to use for the API Server serving certificate. Can be both IP addresses and DNS names.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--certificate-key string

Key used to encrypt the control-plane certificates in the kubeadm-certs Secret.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--dry-run

Don't apply any changes; just output what would be done.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for init

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--node-name string

Specify the node name.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

--skip-certificate-key-print

Don't print the key used to encrypt the control-plane certificates.

--skip-phases strings

List of phases to be skipped

--skip-token-print

Skip printing of the default bootstrap token generated by 'kubeadm init'.

--token string

The token to use for establishing bidirectional trust between nodes and control-plane nodes. The format is [a-z0-9]{6}.[a-z0-9]{16} - e.g. abcdef.0123456789abcdef

--token-ttl duration     Default: 24h0m0s

The duration before the token is automatically deleted (e.g. 1s, 2m, 3h). If set to '0', the token will never expire

--upload-certs

Upload control-plane certificates to the kubeadm-certs Secret.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.31 -

Use this command to invoke single phase of the init workflow

Synopsis

Use this command to invoke single phase of the init workflow

Options

-h, --help

help for phase

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.32 -

Install required addons for passing conformance tests

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase addon [flags]

Options

-h, --help

help for addon

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.33 -

Install all the addons

Synopsis

Install all the addons

kubeadm init phase addon all [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for all

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.34 -

Install the CoreDNS addon to a Kubernetes cluster

Synopsis

Install the CoreDNS addon components via the API server. Please note that although the DNS server is deployed, it will not be scheduled until CNI is installed.

kubeadm init phase addon coredns [flags]

Options

--config string

Path to a kubeadm configuration file.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for coredns

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.35 -

Install the kube-proxy addon to a Kubernetes cluster

Synopsis

Install the kube-proxy addon components via the API server.

kubeadm init phase addon kube-proxy [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for kube-proxy

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.36 -

Generates bootstrap tokens used to join a node to a cluster

Synopsis

Bootstrap tokens are used for establishing bidirectional trust between a node joining the cluster and a control-plane node.

This command makes all the configurations required to make bootstrap tokens works and then creates an initial token.

kubeadm init phase bootstrap-token [flags]

Examples

  # Make all the bootstrap token configurations and create an initial token, functionally
  # equivalent to what generated by kubeadm init.
  kubeadm init phase bootstrap-token

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for bootstrap-token

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--skip-token-print

Skip printing of the default bootstrap token generated by 'kubeadm init'.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.37 -

Certificate generation

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase certs [flags]

Options

-h, --help

help for certs

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.38 -

Generate all certificates

Synopsis

Generate all certificates

kubeadm init phase certs all [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-cert-extra-sans strings

Optional extra Subject Alternative Names (SANs) to use for the API Server serving certificate. Can be both IP addresses and DNS names.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for all

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.39 -

Generate the certificate the apiserver uses to access etcd

Synopsis

Generate the certificate the apiserver uses to access etcd, and save them into apiserver-etcd-client.cert and apiserver-etcd-client.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs apiserver-etcd-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for apiserver-etcd-client

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.40 -

Generate the certificate for the API server to connect to kubelet

Synopsis

Generate the certificate for the API server to connect to kubelet, and save them into apiserver-kubelet-client.cert and apiserver-kubelet-client.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs apiserver-kubelet-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for apiserver-kubelet-client

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.41 -

Generate the certificate for serving the Kubernetes API

Synopsis

Generate the certificate for serving the Kubernetes API, and save them into apiserver.cert and apiserver.key files.

Default SANs are kubernetes, kubernetes.default, kubernetes.default.svc, kubernetes.default.svc.cluster.local, 10.96.0.1, 127.0.0.1

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs apiserver [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-cert-extra-sans strings

Optional extra Subject Alternative Names (SANs) to use for the API Server serving certificate. Can be both IP addresses and DNS names.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for apiserver

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.42 -

Generate the self-signed Kubernetes CA to provision identities for other Kubernetes components

Synopsis

Generate the self-signed Kubernetes CA to provision identities for other Kubernetes components, and save them into ca.cert and ca.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs ca [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for ca

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.43 -

Generate the self-signed CA to provision identities for etcd

Synopsis

Generate the self-signed CA to provision identities for etcd, and save them into etcd/ca.cert and etcd/ca.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs etcd-ca [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for etcd-ca

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.44 -

Generate the certificate for liveness probes to healthcheck etcd

Synopsis

Generate the certificate for liveness probes to healthcheck etcd, and save them into etcd/healthcheck-client.cert and etcd/healthcheck-client.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs etcd-healthcheck-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for etcd-healthcheck-client

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.45 -

Generate the certificate for etcd nodes to communicate with each other

Synopsis

Generate the certificate for etcd nodes to communicate with each other, and save them into etcd/peer.cert and etcd/peer.key files.

Default SANs are localhost, 127.0.0.1, 127.0.0.1, ::1

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs etcd-peer [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for etcd-peer

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.46 -

Generate the certificate for serving etcd

Synopsis

Generate the certificate for serving etcd, and save them into etcd/server.cert and etcd/server.key files.

Default SANs are localhost, 127.0.0.1, 127.0.0.1, ::1

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs etcd-server [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for etcd-server

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.47 -

Generate the self-signed CA to provision identities for front proxy

Synopsis

Generate the self-signed CA to provision identities for front proxy, and save them into front-proxy-ca.cert and front-proxy-ca.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs front-proxy-ca [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for front-proxy-ca

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.48 -

Generate the certificate for the front proxy client

Synopsis

Generate the certificate for the front proxy client, and save them into front-proxy-client.cert and front-proxy-client.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs front-proxy-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for front-proxy-client

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.49 -

Generate a private key for signing service account tokens along with its public key

Synopsis

Generate the private key for signing service account tokens along with its public key, and save them into sa.key and sa.pub files. If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs sa [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

-h, --help

help for sa

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.50 -

Generate all static Pod manifest files necessary to establish the control plane

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase control-plane [flags]

Options

-h, --help

help for control-plane

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.51 -

Generate all static Pod manifest files

Synopsis

Generate all static Pod manifest files

kubeadm init phase control-plane all [flags]

Examples

  # Generates all static Pod manifest files for control plane components,
  # functionally equivalent to what is generated by kubeadm init.
  kubeadm init phase control-plane all
  
  # Generates all static Pod manifest files using options read from a configuration file.
  kubeadm init phase control-plane all --config config.yaml

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--apiserver-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the API Server or override default ones in form of =

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

--controller-manager-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the Controller Manager or override default ones in form of =

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for all

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

--scheduler-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the Scheduler or override default ones in form of =

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.52 -

Generates the kube-apiserver static Pod manifest

Synopsis

Generates the kube-apiserver static Pod manifest

kubeadm init phase control-plane apiserver [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--apiserver-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the API Server or override default ones in form of =

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for apiserver

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.53 -

Generates the kube-controller-manager static Pod manifest

Synopsis

Generates the kube-controller-manager static Pod manifest

kubeadm init phase control-plane controller-manager [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--controller-manager-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the Controller Manager or override default ones in form of =

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for controller-manager

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.54 -

Generates the kube-scheduler static Pod manifest

Synopsis

Generates the kube-scheduler static Pod manifest

kubeadm init phase control-plane scheduler [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for scheduler

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--scheduler-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the Scheduler or override default ones in form of =

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.55 -

Generate static Pod manifest file for local etcd

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase etcd [flags]

Options

-h, --help

help for etcd

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.56 -

Generate the static Pod manifest file for a local, single-node local etcd instance

Synopsis

Generate the static Pod manifest file for a local, single-node local etcd instance

kubeadm init phase etcd local [flags]

Examples

  # Generates the static Pod manifest file for etcd, functionally
  # equivalent to what is generated by kubeadm init.
  kubeadm init phase etcd local
  
  # Generates the static Pod manifest file for etcd using options
  # read from a configuration file.
  kubeadm init phase etcd local --config config.yaml

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for local

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.57 -

Generate all kubeconfig files necessary to establish the control plane and the admin kubeconfig file

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase kubeconfig [flags]

Options

-h, --help

help for kubeconfig

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.58 -

Generate a kubeconfig file for the admin to use and for kubeadm itself

Synopsis

Generate the kubeconfig file for the admin and for kubeadm itself, and save it to admin.conf file.

kubeadm init phase kubeconfig admin [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for admin

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.59 -

Generate all kubeconfig files

Synopsis

Generate all kubeconfig files

kubeadm init phase kubeconfig all [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for all

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.60 -

Generate a kubeconfig file for the controller manager to use

Synopsis

Generate the kubeconfig file for the controller manager to use and save it to controller-manager.conf file

kubeadm init phase kubeconfig controller-manager [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for controller-manager

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.61 -

Generate a kubeconfig file for the kubelet to use only for cluster bootstrapping purposes

Synopsis

Generate the kubeconfig file for the kubelet to use and save it to kubelet.conf file.

Please note that this should only be used for cluster bootstrapping purposes. After your control plane is up, you should request all kubelet credentials from the CSR API.

kubeadm init phase kubeconfig kubelet [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for kubelet

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.62 -

Generate a kubeconfig file for the scheduler to use

Synopsis

Generate the kubeconfig file for the scheduler to use and save it to scheduler.conf file.

kubeadm init phase kubeconfig scheduler [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for scheduler

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.63 -

Updates settings relevant to the kubelet after TLS bootstrap

Synopsis

Updates settings relevant to the kubelet after TLS bootstrap

kubeadm init phase kubelet-finalize [flags]

Examples

  # Updates settings relevant to the kubelet after TLS bootstrap"
  kubeadm init phase kubelet-finalize all --config

Options

-h, --help

help for kubelet-finalize

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.64 -

Run all kubelet-finalize phases

Synopsis

Run all kubelet-finalize phases

kubeadm init phase kubelet-finalize all [flags]

Examples

  # Updates settings relevant to the kubelet after TLS bootstrap"
  kubeadm init phase kubelet-finalize all --config

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for all

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.65 -

Enable kubelet client certificate rotation

Synopsis

Enable kubelet client certificate rotation

kubeadm init phase kubelet-finalize experimental-cert-rotation [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for experimental-cert-rotation

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.66 -

Write kubelet settings and (re)start the kubelet

Synopsis

Write a file with KubeletConfiguration and an environment file with node specific kubelet settings, and then (re)start kubelet.

kubeadm init phase kubelet-start [flags]

Examples

  # Writes a dynamic environment file with kubelet flags from a InitConfiguration file.
  kubeadm init phase kubelet-start --config config.yaml

Options

--config string

Path to a kubeadm configuration file.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

-h, --help

help for kubelet-start

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.67 -

Mark a node as a control-plane

Synopsis

Mark a node as a control-plane

kubeadm init phase mark-control-plane [flags]

Examples

  # Applies control-plane label and taint to the current node, functionally equivalent to what executed by kubeadm init.
  kubeadm init phase mark-control-plane --config config.yaml
  
  # Applies control-plane label and taint to a specific node
  kubeadm init phase mark-control-plane --node-name myNode

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for mark-control-plane

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.68 -

Run pre-flight checks

Synopsis

Run pre-flight checks for kubeadm init.

kubeadm init phase preflight [flags]

Examples

  # Run pre-flight checks for kubeadm init using a config file.
  kubeadm init phase preflight --config kubeadm-config.yaml

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for preflight

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.69 -

Upload certificates to kubeadm-certs

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase upload-certs [flags]

Options

--certificate-key string

Key used to encrypt the control-plane certificates in the kubeadm-certs Secret.

--config string

Path to a kubeadm configuration file.

-h, --help

help for upload-certs

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--skip-certificate-key-print

Don't print the key used to encrypt the control-plane certificates.

--upload-certs

Upload control-plane certificates to the kubeadm-certs Secret.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.70 -

Upload the kubeadm and kubelet configuration to a ConfigMap

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase upload-config [flags]

Options

-h, --help

help for upload-config

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.71 -

Upload all configuration to a config map

Synopsis

Upload all configuration to a config map

kubeadm init phase upload-config all [flags]

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for all

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.72 -

Upload the kubeadm ClusterConfiguration to a ConfigMap

Synopsis

Upload the kubeadm ClusterConfiguration to a ConfigMap called kubeadm-config in the kube-system namespace. This enables correct configuration of system components and a seamless user experience when upgrading.

Alternatively, you can use kubeadm config.

kubeadm init phase upload-config kubeadm [flags]

Examples

  # upload the configuration of your cluster
  kubeadm init phase upload-config --config=myConfig.yaml

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for kubeadm

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.73 -

Upload the kubelet component config to a ConfigMap

Synopsis

Upload kubelet configuration extracted from the kubeadm InitConfiguration object to a ConfigMap of the form kubelet-config-1.X in the cluster, where X is the minor version of the current (API Server) Kubernetes version.

kubeadm init phase upload-config kubelet [flags]

Examples

  # Upload the kubelet configuration from the kubeadm Config file to a ConfigMap in the cluster.
  kubeadm init phase upload-config kubelet --config kubeadm.yaml

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for kubelet

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.74 -

Run this on any machine you wish to join an existing cluster

Synopsis

When joining a kubeadm initialized cluster, we need to establish bidirectional trust. This is split into discovery (having the Node trust the Kubernetes Control Plane) and TLS bootstrap (having the Kubernetes Control Plane trust the Node).

There are 2 main schemes for discovery. The first is to use a shared token along with the IP address of the API server. The second is to provide a file - a subset of the standard kubeconfig file. This file can be a local file or downloaded via an HTTPS URL. The forms are kubeadm join --discovery-token abcdef.1234567890abcdef 1.2.3.4:6443, kubeadm join --discovery-file path/to/file.conf, or kubeadm join --discovery-file https://url/file.conf. Only one form can be used. If the discovery information is loaded from a URL, HTTPS must be used. Also, in that case the host installed CA bundle is used to verify the connection.

If you use a shared token for discovery, you should also pass the --discovery-token-ca-cert-hash flag to validate the public key of the root certificate authority (CA) presented by the Kubernetes Control Plane. The value of this flag is specified as "<hash-type>:<hex-encoded-value>", where the supported hash type is "sha256". The hash is calculated over the bytes of the Subject Public Key Info (SPKI) object (as in RFC7469). This value is available in the output of "kubeadm init" or can be calculated using standard tools. The --discovery-token-ca-cert-hash flag may be repeated multiple times to allow more than one public key.

If you cannot know the CA public key hash ahead of time, you can pass the --discovery-token-unsafe-skip-ca-verification flag to disable this verification. This weakens the kubeadm security model since other nodes can potentially impersonate the Kubernetes Control Plane.

The TLS bootstrap mechanism is also driven via a shared token. This is used to temporarily authenticate with the Kubernetes Control Plane to submit a certificate signing request (CSR) for a locally created key pair. By default, kubeadm will set up the Kubernetes Control Plane to automatically approve these signing requests. This token is passed in with the --tls-bootstrap-token abcdef.1234567890abcdef flag.

Often times the same token is used for both parts. In this case, the --token flag can be used instead of specifying each token individually.

The "join [api-server-endpoint]" command executes the following phases:

preflight              Run join pre-flight checks
control-plane-prepare  Prepare the machine for serving a control plane
  /download-certs        [EXPERIMENTAL] Download certificates shared among control-plane nodes from the kubeadm-certs Secret
  /certs                 Generate the certificates for the new control plane components
  /kubeconfig            Generate the kubeconfig for the new control plane components
  /control-plane         Generate the manifests for the new control plane components
kubelet-start          Write kubelet settings, certificates and (re)start the kubelet
control-plane-join     Join a machine as a control plane instance
  /etcd                  Add a new local etcd member
  /update-status         Register the new control-plane node into the ClusterStatus maintained in the kubeadm-config ConfigMap
  /mark-control-plane    Mark a node as a control-plane
kubeadm join [api-server-endpoint] [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

If the node should host a new control plane instance, the port for the API Server to bind to.

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for join

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--node-name string

Specify the node name.

--skip-phases strings

List of phases to be skipped

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.75 -

Use this command to invoke single phase of the join workflow

Synopsis

Use this command to invoke single phase of the join workflow

Options

-h, --help

help for phase

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.76 -

Join a machine as a control plane instance

Synopsis

Join a machine as a control plane instance

kubeadm join phase control-plane-join [flags]

Examples

  # Joins a machine as a control plane instance
  kubeadm join phase control-plane-join all

Options

-h, --help

help for control-plane-join

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.77 -

Join a machine as a control plane instance

Synopsis

Join a machine as a control plane instance

kubeadm join phase control-plane-join all [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

-h, --help

help for all

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.78 -

Add a new local etcd member

Synopsis

Add a new local etcd member

kubeadm join phase control-plane-join etcd [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for etcd

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.79 -

Mark a node as a control-plane

Synopsis

Mark a node as a control-plane

kubeadm join phase control-plane-join mark-control-plane [flags]

Options

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

-h, --help

help for mark-control-plane

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.80 -

Register the new control-plane node into the ClusterStatus maintained in the kubeadm-config ConfigMap

Synopsis

Register the new control-plane node into the ClusterStatus maintained in the kubeadm-config ConfigMap

kubeadm join phase control-plane-join update-status [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

-h, --help

help for update-status

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.81 -

Prepare the machine for serving a control plane

Synopsis

Prepare the machine for serving a control plane

kubeadm join phase control-plane-prepare [flags]

Examples

  # Prepares the machine for serving a control plane
  kubeadm join phase control-plane-prepare all

Options

-h, --help

help for control-plane-prepare

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.82 -

Prepare the machine for serving a control plane

Synopsis

Prepare the machine for serving a control plane

kubeadm join phase control-plane-prepare all [api-server-endpoint] [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

If the node should host a new control plane instance, the port for the API Server to bind to.

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for all

--node-name string

Specify the node name.

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.83 -

Generate the certificates for the new control plane components

Synopsis

Generate the certificates for the new control plane components

kubeadm join phase control-plane-prepare certs [api-server-endpoint] [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for certs

--node-name string

Specify the node name.

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.84 -

Generate the manifests for the new control plane components

Synopsis

Generate the manifests for the new control plane components

kubeadm join phase control-plane-prepare control-plane [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

If the node should host a new control plane instance, the port for the API Server to bind to.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for control-plane

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.85 -

[EXPERIMENTAL] Download certificates shared among control-plane nodes from the kubeadm-certs Secret

Synopsis

[EXPERIMENTAL] Download certificates shared among control-plane nodes from the kubeadm-certs Secret

kubeadm join phase control-plane-prepare download-certs [api-server-endpoint] [flags]

Options

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for download-certs

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.86 -

Generate the kubeconfig for the new control plane components

Synopsis

Generate the kubeconfig for the new control plane components

kubeadm join phase control-plane-prepare kubeconfig [api-server-endpoint] [flags]

Options

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for kubeconfig

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.87 -

Write kubelet settings, certificates and (re)start the kubelet

Synopsis

Write a file with KubeletConfiguration and an environment file with node specific kubelet settings, and then (re)start kubelet.

kubeadm join phase kubelet-start [api-server-endpoint] [flags]

Options

--config string

Path to kubeadm config file.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for kubelet-start

--node-name string

Specify the node name.

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.88 -

Run join pre-flight checks

Synopsis

Run pre-flight checks for kubeadm join.

kubeadm join phase preflight [api-server-endpoint] [flags]

Examples

  # Run join pre-flight checks using a config file.
  kubeadm join phase preflight --config kubeadm-config.yaml

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

If the node should host a new control plane instance, the port for the API Server to bind to.

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for preflight

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--node-name string

Specify the node name.

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.89 -

Kubeconfig file utilities

Synopsis

Kubeconfig file utilities.

Alpha Disclaimer: this command is currently alpha.

Options

-h, --help

help for kubeconfig

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.90 -

Output a kubeconfig file for an additional user

Synopsis

Output a kubeconfig file for an additional user.

Alpha Disclaimer: this command is currently alpha.

kubeadm kubeconfig user [flags]

Examples

  # Output a kubeconfig file for an additional user named foo using a kubeadm config file bar
  kubeadm alpha kubeconfig user --client-name=foo --config=bar

Options

--client-name string

The name of user. It will be used as the CN if client certificates are created

--config string

Path to a kubeadm configuration file.

-h, --help

help for user

--org strings

The orgnizations of the client certificate. It will be used as the O if client certificates are created

--token string

The token that should be used as the authentication mechanism for this kubeconfig, instead of client certificates

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.91 -

Performs a best effort revert of changes made to this host by 'kubeadm init' or 'kubeadm join'

Synopsis

Performs a best effort revert of changes made to this host by 'kubeadm init' or 'kubeadm join'

The "reset" command executes the following phases:

preflight              Run reset pre-flight checks
update-cluster-status  Remove this node from the ClusterStatus object.
remove-etcd-member     Remove a local etcd member.
cleanup-node           Run cleanup node.
kubeadm reset [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path to the directory where the certificates are stored. If specified, clean this directory.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

-f, --force

Reset the node without prompting for confirmation.

-h, --help

help for reset

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--skip-phases strings

List of phases to be skipped

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.92 -

Use this command to invoke single phase of the reset workflow

Synopsis

Use this command to invoke single phase of the reset workflow

Options

-h, --help

help for phase

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.93 -

Run cleanup node.

Synopsis

Run cleanup node.

kubeadm reset phase cleanup-node [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path to the directory where the certificates are stored. If specified, clean this directory.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

-h, --help

help for cleanup-node

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.94 -

Run reset pre-flight checks

Synopsis

Run pre-flight checks for kubeadm reset.

kubeadm reset phase preflight [flags]

Options

-f, --force

Reset the node without prompting for confirmation.

-h, --help

help for preflight

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.95 -

Remove a local etcd member.

Synopsis

Remove a local etcd member for a control plane node.

kubeadm reset phase remove-etcd-member [flags]

Options

-h, --help

help for remove-etcd-member

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.96 -

Remove this node from the ClusterStatus object.

Synopsis

Remove this node from the ClusterStatus object if the node is a control plane node.

kubeadm reset phase update-cluster-status [flags]

Options

-h, --help

help for update-cluster-status

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.97 -

Manage bootstrap tokens

Synopsis

This command manages bootstrap tokens. It is optional and needed only for advanced use cases.

In short, bootstrap tokens are used for establishing bidirectional trust between a client and a server. A bootstrap token can be used when a client (for example a node that is about to join the cluster) needs to trust the server it is talking to. Then a bootstrap token with the "signing" usage can be used. bootstrap tokens can also function as a way to allow short-lived authentication to the API Server (the token serves as a way for the API Server to trust the client), for example for doing the TLS Bootstrap.

What is a bootstrap token more exactly?

  • It is a Secret in the kube-system namespace of type "bootstrap.kubernetes.io/token".
  • A bootstrap token must be of the form "[a-z0-9]{6}.[a-z0-9]{16}". The former part is the public token ID, while the latter is the Token Secret and it must be kept private at all circumstances!
  • The name of the Secret must be named "bootstrap-token-(token-id)".

You can read more about bootstrap tokens here: https://kubernetes.io/docs/admin/bootstrap-tokens/

kubeadm token [flags]

Options

--dry-run

Whether to enable dry-run mode or not

-h, --help

help for token

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.98 -

Create bootstrap tokens on the server

Synopsis

This command will create a bootstrap token for you. You can specify the usages for this token, the "time to live" and an optional human friendly description.

The [token] is the actual token to write. This should be a securely generated random token of the form "[a-z0-9]{6}.[a-z0-9]{16}". If no [token] is given, kubeadm will generate a random token instead.

kubeadm token create [token]

Options

--certificate-key string

When used together with '--print-join-command', print the full 'kubeadm join' flag needed to join the cluster as a control-plane. To create a new certificate key you must use 'kubeadm init phase upload-certs --upload-certs'.

--config string

Path to a kubeadm configuration file.

--description string

A human friendly description of how this token is used.

--groups strings     Default: "system:bootstrappers:kubeadm:default-node-token"

Extra groups that this token will authenticate as when used for authentication. Must match "\Asystem:bootstrappers:[a-z0-9:-]{0,255}[a-z0-9]\z"

-h, --help

help for create

--print-join-command

Instead of printing only the token, print the full 'kubeadm join' flag needed to join the cluster using the token.

--ttl duration     Default: 24h0m0s

The duration before the token is automatically deleted (e.g. 1s, 2m, 3h). If set to '0', the token will never expire

--usages strings     Default: "signing,authentication"

Describes the ways in which this token can be used. You can pass --usages multiple times or provide a comma separated list of options. Valid options: [signing,authentication]

Options inherited from parent commands

--dry-run

Whether to enable dry-run mode or not

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.99 -

Delete bootstrap tokens on the server

Synopsis

This command will delete a list of bootstrap tokens for you.

The [token-value] is the full Token of the form "[a-z0-9]{6}.[a-z0-9]{16}" or the Token ID of the form "[a-z0-9]{6}" to delete.

kubeadm token delete [token-value] ...

Options

-h, --help

help for delete

Options inherited from parent commands

--dry-run

Whether to enable dry-run mode or not

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.100 -

Generate and print a bootstrap token, but do not create it on the server

Synopsis

This command will print out a randomly-generated bootstrap token that can be used with the "init" and "join" commands.

You don't have to use this command in order to generate a token. You can do so yourself as long as it is in the format "[a-z0-9]{6}.[a-z0-9]{16}". This command is provided for convenience to generate tokens in the given format.

You can also use "kubeadm init" without specifying a token and it will generate and print one for you.

kubeadm token generate [flags]

Options

-h, --help

help for generate

Options inherited from parent commands

--dry-run

Whether to enable dry-run mode or not

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.101 -

List bootstrap tokens on the server

Synopsis

This command will list all bootstrap tokens for you.

kubeadm token list [flags]

Options

--allow-missing-template-keys     Default: true

If true, ignore any errors in templates when a field or map key is missing in the template. Only applies to golang and jsonpath output formats.

-o, --experimental-output string     Default: "text"

Output format. One of: text|json|yaml|go-template|go-template-file|template|templatefile|jsonpath|jsonpath-as-json|jsonpath-file.

-h, --help

help for list

--show-managed-fields

If true, keep the managedFields when printing objects in JSON or YAML format.

Options inherited from parent commands

--dry-run

Whether to enable dry-run mode or not

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.102 -

Upgrade your cluster smoothly to a newer version with this command

Synopsis

Upgrade your cluster smoothly to a newer version with this command

kubeadm upgrade [flags]

Options

-h, --help

help for upgrade

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.103 -

Upgrade your Kubernetes cluster to the specified version

Synopsis

Upgrade your Kubernetes cluster to the specified version

kubeadm upgrade apply [version]

Options

--allow-experimental-upgrades

Show unstable versions of Kubernetes as an upgrade alternative and allow upgrading to an alpha/beta/release candidate versions of Kubernetes.

--allow-release-candidate-upgrades

Show release candidate versions of Kubernetes as an upgrade alternative and allow upgrading to a release candidate versions of Kubernetes.

--certificate-renewal     Default: true

Perform the renewal of certificates used by component changed during upgrades.

--config string

Path to a kubeadm configuration file.

--dry-run

Do not change any state, just output what actions would be performed.

--etcd-upgrade     Default: true

Perform the upgrade of etcd.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-f, --force

Force upgrading although some requirements might not be met. This also implies non-interactive mode.

-h, --help

help for apply

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--print-config

Specifies whether the configuration file that will be used in the upgrade should be printed or not.

-y, --yes

Perform the upgrade and do not prompt for confirmation (non-interactive mode).

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.104 -

Show what differences would be applied to existing static pod manifests. See also: kubeadm upgrade apply --dry-run

Synopsis

Show what differences would be applied to existing static pod manifests. See also: kubeadm upgrade apply --dry-run

kubeadm upgrade diff [version] [flags]

Options

--api-server-manifest string     Default: "/etc/kubernetes/manifests/kube-apiserver.yaml"

path to API server manifest

--config string

Path to a kubeadm configuration file.

-c, --context-lines int     Default: 3

How many lines of context in the diff

--controller-manager-manifest string     Default: "/etc/kubernetes/manifests/kube-controller-manager.yaml"

path to controller manifest

-h, --help

help for diff

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--scheduler-manifest string     Default: "/etc/kubernetes/manifests/kube-scheduler.yaml"

path to scheduler manifest

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.105 -

Upgrade commands for a node in the cluster

Synopsis

Upgrade commands for a node in the cluster

The "node" command executes the following phases:

preflight       Run upgrade node pre-flight checks
control-plane   Upgrade the control plane instance deployed on this node, if any
kubelet-config  Upgrade the kubelet configuration for this node
kubeadm upgrade node [flags]

Options

--certificate-renewal     Default: true

Perform the renewal of certificates used by component changed during upgrades.

--dry-run

Do not change any state, just output the actions that would be performed.

--etcd-upgrade     Default: true

Perform the upgrade of etcd.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for node

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--skip-phases strings

List of phases to be skipped

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.106 -

Use this command to invoke single phase of the node workflow

Synopsis

Use this command to invoke single phase of the node workflow

Options

-h, --help

help for phase

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.107 -

Upgrade the control plane instance deployed on this node, if any

Synopsis

Upgrade the control plane instance deployed on this node, if any

kubeadm upgrade node phase control-plane [flags]

Options

--certificate-renewal     Default: true

Perform the renewal of certificates used by component changed during upgrades.

--dry-run

Do not change any state, just output the actions that would be performed.

--etcd-upgrade     Default: true

Perform the upgrade of etcd.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for control-plane

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.108 -

Upgrade the kubelet configuration for this node

Synopsis

Download the kubelet configuration from a ConfigMap of the form "kubelet-config-1.X" in the cluster, where X is the minor version of the kubelet. kubeadm uses the KuberneteVersion field in the kubeadm-config ConfigMap to determine what the desired kubelet version is.

kubeadm upgrade node phase kubelet-config [flags]

Options

--dry-run

Do not change any state, just output the actions that would be performed.

-h, --help

help for kubelet-config

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.109 -

Run upgrade node pre-flight checks

Synopsis

Run pre-flight checks for kubeadm upgrade node.

kubeadm upgrade node phase preflight [flags]

Options

-h, --help

help for preflight

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.110 -

Check which versions are available to upgrade to and validate whether your current cluster is upgradeable. To skip the internet check, pass in the optional [version] parameter

Synopsis

Check which versions are available to upgrade to and validate whether your current cluster is upgradeable. To skip the internet check, pass in the optional [version] parameter

kubeadm upgrade plan [version] [flags]

Options

--allow-experimental-upgrades

Show unstable versions of Kubernetes as an upgrade alternative and allow upgrading to an alpha/beta/release candidate versions of Kubernetes.

--allow-release-candidate-upgrades

Show release candidate versions of Kubernetes as an upgrade alternative and allow upgrading to a release candidate versions of Kubernetes.

--config string

Path to a kubeadm configuration file.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for plan

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--print-config

Specifies whether the configuration file that will be used in the upgrade should be printed or not.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.111 -

Print the version of kubeadm

Synopsis

Print the version of kubeadm

kubeadm version [flags]

Options

-h, --help

help for version

-o, --output string

Output format; available options are 'yaml', 'json' and 'short'

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

1.112 -

All files in this directory are auto-generated from other repos. Do not edit them manually. You must edit them in their upstream repo.

2 - kubeadm init

This command initializes a Kubernetes control-plane node.

Run this command in order to set up the Kubernetes control plane

Synopsis

Run this command in order to set up the Kubernetes control plane

The "init" command executes the following phases:

preflight                    Run pre-flight checks
certs                        Certificate generation
  /ca                          Generate the self-signed Kubernetes CA to provision identities for other Kubernetes components
  /apiserver                   Generate the certificate for serving the Kubernetes API
  /apiserver-kubelet-client    Generate the certificate for the API server to connect to kubelet
  /front-proxy-ca              Generate the self-signed CA to provision identities for front proxy
  /front-proxy-client          Generate the certificate for the front proxy client
  /etcd-ca                     Generate the self-signed CA to provision identities for etcd
  /etcd-server                 Generate the certificate for serving etcd
  /etcd-peer                   Generate the certificate for etcd nodes to communicate with each other
  /etcd-healthcheck-client     Generate the certificate for liveness probes to healthcheck etcd
  /apiserver-etcd-client       Generate the certificate the apiserver uses to access etcd
  /sa                          Generate a private key for signing service account tokens along with its public key
kubeconfig                   Generate all kubeconfig files necessary to establish the control plane and the admin kubeconfig file
  /admin                       Generate a kubeconfig file for the admin to use and for kubeadm itself
  /kubelet                     Generate a kubeconfig file for the kubelet to use *only* for cluster bootstrapping purposes
  /controller-manager          Generate a kubeconfig file for the controller manager to use
  /scheduler                   Generate a kubeconfig file for the scheduler to use
kubelet-start                Write kubelet settings and (re)start the kubelet
control-plane                Generate all static Pod manifest files necessary to establish the control plane
  /apiserver                   Generates the kube-apiserver static Pod manifest
  /controller-manager          Generates the kube-controller-manager static Pod manifest
  /scheduler                   Generates the kube-scheduler static Pod manifest
etcd                         Generate static Pod manifest file for local etcd
  /local                       Generate the static Pod manifest file for a local, single-node local etcd instance
upload-config                Upload the kubeadm and kubelet configuration to a ConfigMap
  /kubeadm                     Upload the kubeadm ClusterConfiguration to a ConfigMap
  /kubelet                     Upload the kubelet component config to a ConfigMap
upload-certs                 Upload certificates to kubeadm-certs
mark-control-plane           Mark a node as a control-plane
bootstrap-token              Generates bootstrap tokens used to join a node to a cluster
kubelet-finalize             Updates settings relevant to the kubelet after TLS bootstrap
  /experimental-cert-rotation  Enable kubelet client certificate rotation
addon                        Install required addons for passing conformance tests
  /coredns                     Install the CoreDNS addon to a Kubernetes cluster
  /kube-proxy                  Install the kube-proxy addon to a Kubernetes cluster
kubeadm init [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--apiserver-cert-extra-sans strings

Optional extra Subject Alternative Names (SANs) to use for the API Server serving certificate. Can be both IP addresses and DNS names.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--certificate-key string

Key used to encrypt the control-plane certificates in the kubeadm-certs Secret.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--dry-run

Don't apply any changes; just output what would be done.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for init

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--node-name string

Specify the node name.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

--skip-certificate-key-print

Don't print the key used to encrypt the control-plane certificates.

--skip-phases strings

List of phases to be skipped

--skip-token-print

Skip printing of the default bootstrap token generated by 'kubeadm init'.

--token string

The token to use for establishing bidirectional trust between nodes and control-plane nodes. The format is [a-z0-9]{6}.[a-z0-9]{16} - e.g. abcdef.0123456789abcdef

--token-ttl duration     Default: 24h0m0s

The duration before the token is automatically deleted (e.g. 1s, 2m, 3h). If set to '0', the token will never expire

--upload-certs

Upload control-plane certificates to the kubeadm-certs Secret.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Init workflow

kubeadm init bootstraps a Kubernetes control-plane node by executing the following steps:

  1. Runs a series of pre-flight checks to validate the system state before making changes. Some checks only trigger warnings, others are considered errors and will exit kubeadm until the problem is corrected or the user specifies --ignore-preflight-errors=<list-of-errors>.

  2. Generates a self-signed CA to set up identities for each component in the cluster. The user can provide their own CA cert and/or key by dropping it in the cert directory configured via --cert-dir (/etc/kubernetes/pki by default). The APIServer certs will have additional SAN entries for any --apiserver-cert-extra-sans arguments, lowercased if necessary.

  3. Writes kubeconfig files in /etc/kubernetes/ for the kubelet, the controller-manager and the scheduler to use to connect to the API server, each with its own identity, as well as an additional kubeconfig file for administration named admin.conf.

  4. Generates static Pod manifests for the API server, controller-manager and scheduler. In case an external etcd is not provided, an additional static Pod manifest is generated for etcd.

    Static Pod manifests are written to /etc/kubernetes/manifests; the kubelet watches this directory for Pods to create on startup.

    Once control plane Pods are up and running, the kubeadm init sequence can continue.

  5. Apply labels and taints to the control-plane node so that no additional workloads will run there.

  6. Generates the token that additional nodes can use to register themselves with a control-plane in the future. Optionally, the user can provide a token via --token, as described in the kubeadm token docs.

  7. Makes all the necessary configurations for allowing node joining with the Bootstrap Tokens and TLS Bootstrap mechanism:

    • Write a ConfigMap for making available all the information required for joining, and set up related RBAC access rules.

    • Let Bootstrap Tokens access the CSR signing API.

    • Configure auto-approval for new CSR requests.

    See kubeadm join for additional info.

  8. Installs a DNS server (CoreDNS) and the kube-proxy addon components via the API server. In Kubernetes version 1.11 and later CoreDNS is the default DNS server. Please note that although the DNS server is deployed, it will not be scheduled until CNI is installed.

    Warning: kube-dns usage with kubeadm is deprecated as of v1.18 and is removed in v1.21.

Using init phases with kubeadm

Kubeadm allows you to create a control-plane node in phases using the kubeadm init phase command.

To view the ordered list of phases and sub-phases you can call kubeadm init --help. The list will be located at the top of the help screen and each phase will have a description next to it. Note that by calling kubeadm init all of the phases and sub-phases will be executed in this exact order.

Some phases have unique flags, so if you want to have a look at the list of available options add --help, for example:

sudo kubeadm init phase control-plane controller-manager --help

You can also use --help to see the list of sub-phases for a certain parent phase:

sudo kubeadm init phase control-plane --help

kubeadm init also exposes a flag called --skip-phases that can be used to skip certain phases. The flag accepts a list of phase names and the names can be taken from the above ordered list.

An example:

sudo kubeadm init phase control-plane all --config=configfile.yaml
sudo kubeadm init phase etcd local --config=configfile.yaml
# you can now modify the control plane and etcd manifest files
sudo kubeadm init --skip-phases=control-plane,etcd --config=configfile.yaml

What this example would do is write the manifest files for the control plane and etcd in /etc/kubernetes/manifests based on the configuration in configfile.yaml. This allows you to modify the files and then skip these phases using --skip-phases. By calling the last command you will create a control plane node with the custom manifest files.

Using kubeadm init with a configuration file

Caution: The config file is still considered beta and may change in future versions.

It's possible to configure kubeadm init with a configuration file instead of command line flags, and some more advanced features may only be available as configuration file options. This file is passed using the --config flag and it must contain a ClusterConfiguration structure and optionally more structures separated by ---\n Mixing --config with others flags may not be allowed in some cases.

The default configuration can be printed out using the kubeadm config print command.

If your configuration is not using the latest version it is recommended that you migrate using the kubeadm config migrate command.

For more information on the fields and usage of the configuration you can navigate to our API reference page and pick a version from the list.

Adding kube-proxy parameters

For information about kube-proxy parameters in the kubeadm configuration see:

For information about enabling IPVS mode with kubeadm see:

Passing custom flags to control plane components

For information about passing flags to control plane components see:

Using custom images

By default, kubeadm pulls images from k8s.gcr.io. If the requested Kubernetes version is a CI label (such as ci/latest) gcr.io/kubernetes-ci-images is used.

You can override this behavior by using kubeadm with a configuration file. Allowed customization are:

  • To provide an alternative imageRepository to be used instead of k8s.gcr.io.
  • To set useHyperKubeImage to true to use the HyperKube image.
  • To provide a specific imageRepository and imageTag for etcd or DNS add-on.

Please note that the configuration field kubernetesVersion or the command line flag --kubernetes-version affect the version of the images.

Uploading control-plane certificates to the cluster

By adding the flag --upload-certs to kubeadm init you can temporary upload the control-plane certificates to a Secret in the cluster. Please note that this Secret will expire automatically after 2 hours. The certificates are encrypted using a 32byte key that can be specified using --certificate-key. The same key can be used to download the certificates when additional control-plane nodes are joining, by passing --control-plane and --certificate-key to kubeadm join.

The following phase command can be used to re-upload the certificates after expiration:

kubeadm init phase upload-certs --upload-certs --certificate-key=SOME_VALUE --config=SOME_YAML_FILE

If the flag --certificate-key is not passed to kubeadm init and kubeadm init phase upload-certs a new key will be generated automatically.

The following command can be used to generate a new key on demand:

kubeadm certs certificate-key

Certificate management with kubeadm

For detailed information on certificate management with kubeadm see Certificate Management with kubeadm. The document includes information about using external CA, custom certificates and certificate renewal.

Managing the kubeadm drop-in file for the kubelet

The kubeadm package ships with a configuration file for running the kubelet by systemd. Note that the kubeadm CLI never touches this drop-in file. This drop-in file is part of the kubeadm DEB/RPM package.

For further information, see Managing the kubeadm drop-in file for systemd.

Use kubeadm with CRI runtimes

By default kubeadm attempts to detect your container runtime. For more details on this detection, see the kubeadm CRI installation guide.

Setting the node name

By default, kubeadm assigns a node name based on a machine's host address. You can override this setting with the --node-name flag. The flag passes the appropriate --hostname-override value to the kubelet.

Be aware that overriding the hostname can interfere with cloud providers.

Running kubeadm without an internet connection

For running kubeadm without an internet connection you have to pre-pull the required control-plane images.

You can list and pull the images using the kubeadm config images sub-command:

kubeadm config images list
kubeadm config images pull

All images that kubeadm requires such as k8s.gcr.io/kube-*, k8s.gcr.io/etcd and k8s.gcr.io/pause support multiple architectures.

Automating kubeadm

Rather than copying the token you obtained from kubeadm init to each node, as in the basic kubeadm tutorial, you can parallelize the token distribution for easier automation. To implement this automation, you must know the IP address that the control-plane node will have after it is started, or use a DNS name or an address of a load balancer.

  1. Generate a token. This token must have the form <6 character string>.<16 character string>. More formally, it must match the regex: [a-z0-9]{6}\.[a-z0-9]{16}.

    kubeadm can generate a token for you:

     kubeadm token generate
    
  2. Start both the control-plane node and the worker nodes concurrently with this token. As they come up they should find each other and form the cluster. The same --token argument can be used on both kubeadm init and kubeadm join.

  3. Similar can be done for --certificate-key when joining additional control-plane nodes. The key can be generated using:

    kubeadm certs certificate-key
    

Once the cluster is up, you can grab the admin credentials from the control-plane node at /etc/kubernetes/admin.conf and use that to talk to the cluster.

Note that this style of bootstrap has some relaxed security guarantees because it does not allow the root CA hash to be validated with --discovery-token-ca-cert-hash (since it's not generated when the nodes are provisioned). For details, see the kubeadm join.

What's next

  • kubeadm init phase to understand more about kubeadm init phases
  • kubeadm join to bootstrap a Kubernetes worker node and join it to the cluster
  • kubeadm upgrade to upgrade a Kubernetes cluster to a newer version
  • kubeadm reset to revert any changes made to this host by kubeadm init or kubeadm join

3 - kubeadm join

This command initializes a Kubernetes worker node and joins it to the cluster.

Run this on any machine you wish to join an existing cluster

Synopsis

When joining a kubeadm initialized cluster, we need to establish bidirectional trust. This is split into discovery (having the Node trust the Kubernetes Control Plane) and TLS bootstrap (having the Kubernetes Control Plane trust the Node).

There are 2 main schemes for discovery. The first is to use a shared token along with the IP address of the API server. The second is to provide a file - a subset of the standard kubeconfig file. This file can be a local file or downloaded via an HTTPS URL. The forms are kubeadm join --discovery-token abcdef.1234567890abcdef 1.2.3.4:6443, kubeadm join --discovery-file path/to/file.conf, or kubeadm join --discovery-file https://url/file.conf. Only one form can be used. If the discovery information is loaded from a URL, HTTPS must be used. Also, in that case the host installed CA bundle is used to verify the connection.

If you use a shared token for discovery, you should also pass the --discovery-token-ca-cert-hash flag to validate the public key of the root certificate authority (CA) presented by the Kubernetes Control Plane. The value of this flag is specified as "<hash-type>:<hex-encoded-value>", where the supported hash type is "sha256". The hash is calculated over the bytes of the Subject Public Key Info (SPKI) object (as in RFC7469). This value is available in the output of "kubeadm init" or can be calculated using standard tools. The --discovery-token-ca-cert-hash flag may be repeated multiple times to allow more than one public key.

If you cannot know the CA public key hash ahead of time, you can pass the --discovery-token-unsafe-skip-ca-verification flag to disable this verification. This weakens the kubeadm security model since other nodes can potentially impersonate the Kubernetes Control Plane.

The TLS bootstrap mechanism is also driven via a shared token. This is used to temporarily authenticate with the Kubernetes Control Plane to submit a certificate signing request (CSR) for a locally created key pair. By default, kubeadm will set up the Kubernetes Control Plane to automatically approve these signing requests. This token is passed in with the --tls-bootstrap-token abcdef.1234567890abcdef flag.

Often times the same token is used for both parts. In this case, the --token flag can be used instead of specifying each token individually.

The "join [api-server-endpoint]" command executes the following phases:

preflight              Run join pre-flight checks
control-plane-prepare  Prepare the machine for serving a control plane
  /download-certs        [EXPERIMENTAL] Download certificates shared among control-plane nodes from the kubeadm-certs Secret
  /certs                 Generate the certificates for the new control plane components
  /kubeconfig            Generate the kubeconfig for the new control plane components
  /control-plane         Generate the manifests for the new control plane components
kubelet-start          Write kubelet settings, certificates and (re)start the kubelet
control-plane-join     Join a machine as a control plane instance
  /etcd                  Add a new local etcd member
  /update-status         Register the new control-plane node into the ClusterStatus maintained in the kubeadm-config ConfigMap
  /mark-control-plane    Mark a node as a control-plane
kubeadm join [api-server-endpoint] [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

If the node should host a new control plane instance, the port for the API Server to bind to.

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for join

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--node-name string

Specify the node name.

--skip-phases strings

List of phases to be skipped

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

The join workflow

kubeadm join bootstraps a Kubernetes worker node or a control-plane node and adds it to the cluster. This action consists of the following steps for worker nodes:

  1. kubeadm downloads necessary cluster information from the API server. By default, it uses the bootstrap token and the CA key hash to verify the authenticity of that data. The root CA can also be discovered directly via a file or URL.

  2. Once the cluster information is known, kubelet can start the TLS bootstrapping process.

    The TLS bootstrap uses the shared token to temporarily authenticate with the Kubernetes API server to submit a certificate signing request (CSR); by default the control plane signs this CSR request automatically.

  3. Finally, kubeadm configures the local kubelet to connect to the API server with the definitive identity assigned to the node.

For control-plane nodes additional steps are performed:

  1. Downloading certificates shared among control-plane nodes from the cluster (if explicitly requested by the user).

  2. Generating control-plane component manifests, certificates and kubeconfig.

  3. Adding new local etcd member.

  4. Adding this node to the ClusterStatus of the kubeadm cluster.

Using join phases with kubeadm

Kubeadm allows you join a node to the cluster in phases using kubeadm join phase.

To view the ordered list of phases and sub-phases you can call kubeadm join --help. The list will be located at the top of the help screen and each phase will have a description next to it. Note that by calling kubeadm join all of the phases and sub-phases will be executed in this exact order.

Some phases have unique flags, so if you want to have a look at the list of available options add --help, for example:

kubeadm join phase kubelet-start --help

Similar to the kubeadm init phase command, kubeadm join phase allows you to skip a list of phases using the --skip-phases flag.

For example:

sudo kubeadm join --skip-phases=preflight --config=config.yaml

Discovering what cluster CA to trust

The kubeadm discovery has several options, each with security tradeoffs. The right method for your environment depends on how you provision nodes and the security expectations you have about your network and node lifecycles.

Token-based discovery with CA pinning

This is the default mode in kubeadm. In this mode, kubeadm downloads the cluster configuration (including root CA) and validates it using the token as well as validating that the root CA public key matches the provided hash and that the API server certificate is valid under the root CA.

The CA key hash has the format sha256:<hex_encoded_hash>. By default, the hash value is returned in the kubeadm join command printed at the end of kubeadm init or in the output of kubeadm token create --print-join-command. It is in a standard format (see RFC7469) and can also be calculated by 3rd party tools or provisioning systems. For example, using the OpenSSL CLI:

openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'

Example kubeadm join commands:

For worker nodes:

kubeadm join --discovery-token abcdef.1234567890abcdef --discovery-token-ca-cert-hash sha256:1234..cdef 1.2.3.4:6443

For control-plane nodes:

kubeadm join --discovery-token abcdef.1234567890abcdef --discovery-token-ca-cert-hash sha256:1234..cdef --control-plane 1.2.3.4:6443

You can also call join for a control-plane node with --certificate-key to copy certificates to this node, if the kubeadm init command was called with --upload-certs.

Advantages:

  • Allows bootstrapping nodes to securely discover a root of trust for the control-plane node even if other worker nodes or the network are compromised.

  • Convenient to execute manually since all of the information required fits into a single kubeadm join command.

Disadvantages:

  • The CA hash is not normally known until the control-plane node has been provisioned, which can make it more difficult to build automated provisioning tools that use kubeadm. By generating your CA in beforehand, you may workaround this limitation.

Token-based discovery without CA pinning

This mode relies only on the symmetric token to sign (HMAC-SHA256) the discovery information that establishes the root of trust for the control-plane. To use the mode the joining nodes must skip the hash validation of the CA public key, using --discovery-token-unsafe-skip-ca-verification. You should consider using one of the other modes if possible.

Example kubeadm join command:

kubeadm join --token abcdef.1234567890abcdef --discovery-token-unsafe-skip-ca-verification 1.2.3.4:6443

Advantages:

  • Still protects against many network-level attacks.

  • The token can be generated ahead of time and shared with the control-plane node and worker nodes, which can then bootstrap in parallel without coordination. This allows it to be used in many provisioning scenarios.

Disadvantages:

  • If an attacker is able to steal a bootstrap token via some vulnerability, they can use that token (along with network-level access) to impersonate the control-plane node to other bootstrapping nodes. This may or may not be an appropriate tradeoff in your environment.

File or HTTPS-based discovery

This provides an out-of-band way to establish a root of trust between the control-plane node and bootstrapping nodes. Consider using this mode if you are building automated provisioning using kubeadm. The format of the discovery file is a regular Kubernetes kubeconfig file.

In case the discovery file does not contain credentials, the TLS discovery token will be used.

Example kubeadm join commands:

  • kubeadm join --discovery-file path/to/file.conf (local file)

  • kubeadm join --discovery-file https://url/file.conf (remote HTTPS URL)

Advantages:

  • Allows bootstrapping nodes to securely discover a root of trust for the control-plane node even if the network or other worker nodes are compromised.

Disadvantages:

  • Requires that you have some way to carry the discovery information from the control-plane node to the bootstrapping nodes. If the discovery file contains credentials you must keep it secret and transfer it over a secure channel. This might be possible with your cloud provider or provisioning tool.

Securing your installation even more

The defaults for kubeadm may not work for everyone. This section documents how to tighten up a kubeadm installation at the cost of some usability.

Turning off auto-approval of node client certificates

By default, there is a CSR auto-approver enabled that basically approves any client certificate request for a kubelet when a Bootstrap Token was used when authenticating. If you don't want the cluster to automatically approve kubelet client certs, you can turn it off by executing this command:

kubectl delete clusterrolebinding kubeadm:node-autoapprove-bootstrap

After that, kubeadm join will block until the admin has manually approved the CSR in flight:

kubectl get csr

The output is similar to this:

NAME                                                   AGE       REQUESTOR                 CONDITION
node-csr-c69HXe7aYcqkS1bKmH4faEnHAWxn6i2bHZ2mD04jZyQ   18s       system:bootstrap:878f07   Pending
kubectl certificate approve node-csr-c69HXe7aYcqkS1bKmH4faEnHAWxn6i2bHZ2mD04jZyQ

The output is similar to this:

certificatesigningrequest "node-csr-c69HXe7aYcqkS1bKmH4faEnHAWxn6i2bHZ2mD04jZyQ" approved
kubectl get csr

The output is similar to this:

NAME                                                   AGE       REQUESTOR                 CONDITION
node-csr-c69HXe7aYcqkS1bKmH4faEnHAWxn6i2bHZ2mD04jZyQ   1m        system:bootstrap:878f07   Approved,Issued

This forces the workflow that kubeadm join will only succeed if kubectl certificate approve has been run.

Turning off public access to the cluster-info ConfigMap

In order to achieve the joining flow using the token as the only piece of validation information, a ConfigMap with some data needed for validation of the control-plane node's identity is exposed publicly by default. While there is no private data in this ConfigMap, some users might wish to turn it off regardless. Doing so will disable the ability to use the --discovery-token flag of the kubeadm join flow. Here are the steps to do so:

  • Fetch the cluster-info file from the API Server:
kubectl -n kube-public get cm cluster-info -o yaml | grep "kubeconfig:" -A11 | grep "apiVersion" -A10 | sed "s/    //" | tee cluster-info.yaml

The output is similar to this:

apiVersion: v1
kind: Config
clusters:
- cluster:
    certificate-authority-data: <ca-cert>
    server: https://<ip>:<port>
  name: ""
contexts: []
current-context: ""
preferences: {}
users: []
  • Use the cluster-info.yaml file as an argument to kubeadm join --discovery-file.

  • Turn off public access to the cluster-info ConfigMap:

kubectl -n kube-public delete rolebinding kubeadm:bootstrap-signer-clusterinfo

These commands should be run after kubeadm init but before kubeadm join.

Using kubeadm join with a configuration file

Caution: The config file is still considered beta and may change in future versions.

It's possible to configure kubeadm join with a configuration file instead of command line flags, and some more advanced features may only be available as configuration file options. This file is passed using the --config flag and it must contain a JoinConfiguration structure. Mixing --config with others flags may not be allowed in some cases.

The default configuration can be printed out using the kubeadm config print command.

If your configuration is not using the latest version it is recommended that you migrate using the kubeadm config migrate command.

For more information on the fields and usage of the configuration you can navigate to our API reference page and pick a version from the list.

What's next

4 - kubeadm upgrade

kubeadm upgrade is a user-friendly command that wraps complex upgrading logic behind one command, with support for both planning an upgrade and actually performing it.

kubeadm upgrade guidance

The steps for performing a upgrade using kubeadm are outlined in this document. For older versions of kubeadm, please refer to older documentation sets of the Kubernetes website.

You can use kubeadm upgrade diff to see the changes that would be applied to static pod manifests.

In Kubernetes v1.15.0 and later, kubeadm upgrade apply and kubeadm upgrade node will also automatically renew the kubeadm managed certificates on this node, including those stored in kubeconfig files. To opt-out, it is possible to pass the flag --certificate-renewal=false. For more details about certificate renewal see the certificate management documentation.

Note: The commands kubeadm upgrade apply and kubeadm upgrade plan have a legacy --config flag which makes it possible to reconfigure the cluster, while performing planning or upgrade of that particular control-plane node. Please be aware that the upgrade workflow was not designed for this scenario and there are reports of unexpected results.

kubeadm upgrade plan

Check which versions are available to upgrade to and validate whether your current cluster is upgradeable. To skip the internet check, pass in the optional [version] parameter

Synopsis

Check which versions are available to upgrade to and validate whether your current cluster is upgradeable. To skip the internet check, pass in the optional [version] parameter

kubeadm upgrade plan [version] [flags]

Options

--allow-experimental-upgrades

Show unstable versions of Kubernetes as an upgrade alternative and allow upgrading to an alpha/beta/release candidate versions of Kubernetes.

--allow-release-candidate-upgrades

Show release candidate versions of Kubernetes as an upgrade alternative and allow upgrading to a release candidate versions of Kubernetes.

--config string

Path to a kubeadm configuration file.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for plan

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--print-config

Specifies whether the configuration file that will be used in the upgrade should be printed or not.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm upgrade apply

Upgrade your Kubernetes cluster to the specified version

Synopsis

Upgrade your Kubernetes cluster to the specified version

kubeadm upgrade apply [version]

Options

--allow-experimental-upgrades

Show unstable versions of Kubernetes as an upgrade alternative and allow upgrading to an alpha/beta/release candidate versions of Kubernetes.

--allow-release-candidate-upgrades

Show release candidate versions of Kubernetes as an upgrade alternative and allow upgrading to a release candidate versions of Kubernetes.

--certificate-renewal     Default: true

Perform the renewal of certificates used by component changed during upgrades.

--config string

Path to a kubeadm configuration file.

--dry-run

Do not change any state, just output what actions would be performed.

--etcd-upgrade     Default: true

Perform the upgrade of etcd.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-f, --force

Force upgrading although some requirements might not be met. This also implies non-interactive mode.

-h, --help

help for apply

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--print-config

Specifies whether the configuration file that will be used in the upgrade should be printed or not.

-y, --yes

Perform the upgrade and do not prompt for confirmation (non-interactive mode).

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm upgrade diff

Show what differences would be applied to existing static pod manifests. See also: kubeadm upgrade apply --dry-run

Synopsis

Show what differences would be applied to existing static pod manifests. See also: kubeadm upgrade apply --dry-run

kubeadm upgrade diff [version] [flags]

Options

--api-server-manifest string     Default: "/etc/kubernetes/manifests/kube-apiserver.yaml"

path to API server manifest

--config string

Path to a kubeadm configuration file.

-c, --context-lines int     Default: 3

How many lines of context in the diff

--controller-manager-manifest string     Default: "/etc/kubernetes/manifests/kube-controller-manager.yaml"

path to controller manifest

-h, --help

help for diff

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--scheduler-manifest string     Default: "/etc/kubernetes/manifests/kube-scheduler.yaml"

path to scheduler manifest

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm upgrade node

Upgrade commands for a node in the cluster

Synopsis

Upgrade commands for a node in the cluster

The "node" command executes the following phases:

preflight       Run upgrade node pre-flight checks
control-plane   Upgrade the control plane instance deployed on this node, if any
kubelet-config  Upgrade the kubelet configuration for this node
kubeadm upgrade node [flags]

Options

--certificate-renewal     Default: true

Perform the renewal of certificates used by component changed during upgrades.

--dry-run

Do not change any state, just output the actions that would be performed.

--etcd-upgrade     Default: true

Perform the upgrade of etcd.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for node

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--skip-phases strings

List of phases to be skipped

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

What's next

  • kubeadm config if you initialized your cluster using kubeadm v1.7.x or lower, to configure your cluster for kubeadm upgrade

5 - kubeadm config

During kubeadm init, kubeadm uploads the ClusterConfiguration object to your cluster in a ConfigMap called kubeadm-config in the kube-system namespace. This configuration is then read during kubeadm join, kubeadm reset and kubeadm upgrade. To view this ConfigMap call kubeadm config view.

You can use kubeadm config print to print the default configuration and kubeadm config migrate to convert your old configuration files to a newer version. kubeadm config images list and kubeadm config images pull can be used to list and pull the images that kubeadm requires.

For more information navigate to Using kubeadm init with a configuration file or Using kubeadm join with a configuration file.

You can also configure several kubelet-configuration options with kubeadm init. These options will be the same on any node in your cluster. See Configuring each kubelet in your cluster using kubeadm for details.

In Kubernetes v1.13.0 and later to list/pull kube-dns images instead of the CoreDNS image the --config method described here has to be used.

kubeadm config print

Print configuration

Synopsis

This command prints configurations for subcommands provided. For details, see: https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2

kubeadm config print [flags]

Options

-h, --help

help for print

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm config print init-defaults

Print default init configuration, that can be used for 'kubeadm init'

Synopsis

This command prints objects such as the default init configuration that is used for 'kubeadm init'.

Note that sensitive values like the Bootstrap Token fields are replaced with placeholder values like "abcdef.0123456789abcdef" in order to pass validation but not perform the real computation for creating a token.

kubeadm config print init-defaults [flags]

Options

--component-configs strings

A comma-separated list for component config API objects to print the default values for. Available values: [KubeProxyConfiguration KubeletConfiguration]. If this flag is not set, no component configs will be printed.

-h, --help

help for init-defaults

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm config print join-defaults

Print default join configuration, that can be used for 'kubeadm join'

Synopsis

This command prints objects such as the default join configuration that is used for 'kubeadm join'.

Note that sensitive values like the Bootstrap Token fields are replaced with placeholder values like "abcdef.0123456789abcdef" in order to pass validation but not perform the real computation for creating a token.

kubeadm config print join-defaults [flags]

Options

--component-configs strings

A comma-separated list for component config API objects to print the default values for. Available values: [KubeProxyConfiguration KubeletConfiguration]. If this flag is not set, no component configs will be printed.

-h, --help

help for join-defaults

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm config migrate

Read an older version of the kubeadm configuration API types from a file, and output the similar config object for the newer version

Synopsis

This command lets you convert configuration objects of older versions to the latest supported version, locally in the CLI tool without ever touching anything in the cluster. In this version of kubeadm, the following API versions are supported:

  • kubeadm.k8s.io/v1beta2

Further, kubeadm can only write out config of version "kubeadm.k8s.io/v1beta2", but read both types. So regardless of what version you pass to the --old-config parameter here, the API object will be read, deserialized, defaulted, converted, validated, and re-serialized when written to stdout or --new-config if specified.

In other words, the output of this command is what kubeadm actually would read internally if you submitted this file to "kubeadm init"

kubeadm config migrate [flags]

Options

-h, --help

help for migrate

--new-config string

Path to the resulting equivalent kubeadm config file using the new API version. Optional, if not specified output will be sent to STDOUT.

--old-config string

Path to the kubeadm config file that is using an old API version and should be converted. This flag is mandatory.

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm config images list

Print a list of images kubeadm will use. The configuration file is used in case any images or image repositories are customized

Synopsis

Print a list of images kubeadm will use. The configuration file is used in case any images or image repositories are customized

kubeadm config images list [flags]

Options

--allow-missing-template-keys     Default: true

If true, ignore any errors in templates when a field or map key is missing in the template. Only applies to golang and jsonpath output formats.

--config string

Path to a kubeadm configuration file.

-o, --experimental-output string     Default: "text"

Output format. One of: text|json|yaml|go-template|go-template-file|template|templatefile|jsonpath|jsonpath-as-json|jsonpath-file.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for list

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--show-managed-fields

If true, keep the managedFields when printing objects in JSON or YAML format.

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm config images pull

Pull images used by kubeadm

Synopsis

Pull images used by kubeadm

kubeadm config images pull [flags]

Options

--config string

Path to a kubeadm configuration file.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for pull

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

What's next

6 - kubeadm reset

Performs a best effort revert of changes made by kubeadm init or kubeadm join.

Performs a best effort revert of changes made to this host by 'kubeadm init' or 'kubeadm join'

Synopsis

Performs a best effort revert of changes made to this host by 'kubeadm init' or 'kubeadm join'

The "reset" command executes the following phases:

preflight              Run reset pre-flight checks
update-cluster-status  Remove this node from the ClusterStatus object.
remove-etcd-member     Remove a local etcd member.
cleanup-node           Run cleanup node.
kubeadm reset [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path to the directory where the certificates are stored. If specified, clean this directory.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

-f, --force

Reset the node without prompting for confirmation.

-h, --help

help for reset

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--skip-phases strings

List of phases to be skipped

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Reset workflow

kubeadm reset is responsible for cleaning up a node local file system from files that were created using the kubeadm init or kubeadm join commands. For control-plane nodes reset also removes the local stacked etcd member of this node from the etcd cluster and also removes this node's information from the kubeadm ClusterStatus object. ClusterStatus is a kubeadm managed Kubernetes API object that holds a list of kube-apiserver endpoints.

kubeadm reset phase can be used to execute the separate phases of the above workflow. To skip a list of phases you can use the --skip-phases flag, which works in a similar way to the kubeadm join and kubeadm init phase runners.

External etcd clean up

kubeadm reset will not delete any etcd data if external etcd is used. This means that if you run kubeadm init again using the same etcd endpoints, you will see state from previous clusters.

To wipe etcd data it is recommended you use a client like etcdctl, such as:

etcdctl del "" --prefix

See the etcd documentation for more information.

What's next

  • kubeadm init to bootstrap a Kubernetes control-plane node
  • kubeadm join to bootstrap a Kubernetes worker node and join it to the cluster

7 - kubeadm token

Bootstrap tokens are used for establishing bidirectional trust between a node joining the cluster and a control-plane node, as described in authenticating with bootstrap tokens.

kubeadm init creates an initial token with a 24-hour TTL. The following commands allow you to manage such a token and also to create and manage new ones.

kubeadm token create

Create bootstrap tokens on the server

Synopsis

This command will create a bootstrap token for you. You can specify the usages for this token, the "time to live" and an optional human friendly description.

The [token] is the actual token to write. This should be a securely generated random token of the form "[a-z0-9]{6}.[a-z0-9]{16}". If no [token] is given, kubeadm will generate a random token instead.

kubeadm token create [token]

Options

--certificate-key string

When used together with '--print-join-command', print the full 'kubeadm join' flag needed to join the cluster as a control-plane. To create a new certificate key you must use 'kubeadm init phase upload-certs --upload-certs'.

--config string

Path to a kubeadm configuration file.

--description string

A human friendly description of how this token is used.

--groups strings     Default: "system:bootstrappers:kubeadm:default-node-token"

Extra groups that this token will authenticate as when used for authentication. Must match "\Asystem:bootstrappers:[a-z0-9:-]{0,255}[a-z0-9]\z"

-h, --help

help for create

--print-join-command

Instead of printing only the token, print the full 'kubeadm join' flag needed to join the cluster using the token.

--ttl duration     Default: 24h0m0s

The duration before the token is automatically deleted (e.g. 1s, 2m, 3h). If set to '0', the token will never expire

--usages strings     Default: "signing,authentication"

Describes the ways in which this token can be used. You can pass --usages multiple times or provide a comma separated list of options. Valid options: [signing,authentication]

Options inherited from parent commands

--dry-run

Whether to enable dry-run mode or not

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm token delete

Delete bootstrap tokens on the server

Synopsis

This command will delete a list of bootstrap tokens for you.

The [token-value] is the full Token of the form "[a-z0-9]{6}.[a-z0-9]{16}" or the Token ID of the form "[a-z0-9]{6}" to delete.

kubeadm token delete [token-value] ...

Options

-h, --help

help for delete

Options inherited from parent commands

--dry-run

Whether to enable dry-run mode or not

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm token generate

Generate and print a bootstrap token, but do not create it on the server

Synopsis

This command will print out a randomly-generated bootstrap token that can be used with the "init" and "join" commands.

You don't have to use this command in order to generate a token. You can do so yourself as long as it is in the format "[a-z0-9]{6}.[a-z0-9]{16}". This command is provided for convenience to generate tokens in the given format.

You can also use "kubeadm init" without specifying a token and it will generate and print one for you.

kubeadm token generate [flags]

Options

-h, --help

help for generate

Options inherited from parent commands

--dry-run

Whether to enable dry-run mode or not

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm token list

List bootstrap tokens on the server

Synopsis

This command will list all bootstrap tokens for you.

kubeadm token list [flags]

Options

--allow-missing-template-keys     Default: true

If true, ignore any errors in templates when a field or map key is missing in the template. Only applies to golang and jsonpath output formats.

-o, --experimental-output string     Default: "text"

Output format. One of: text|json|yaml|go-template|go-template-file|template|templatefile|jsonpath|jsonpath-as-json|jsonpath-file.

-h, --help

help for list

--show-managed-fields

If true, keep the managedFields when printing objects in JSON or YAML format.

Options inherited from parent commands

--dry-run

Whether to enable dry-run mode or not

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

What's next

  • kubeadm join to bootstrap a Kubernetes worker node and join it to the cluster

8 - kubeadm version

This command prints the version of kubeadm.

Print the version of kubeadm

Synopsis

Print the version of kubeadm

kubeadm version [flags]

Options

-h, --help

help for version

-o, --output string

Output format; available options are 'yaml', 'json' and 'short'

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

9 - kubeadm alpha

Caution: kubeadm alpha provides a preview of a set of features made available for gathering feedback from the community. Please try it out and give us feedback!

Currently there are no experimental commands under kubeadm alpha.

What's next

  • kubeadm init to bootstrap a Kubernetes control-plane node
  • kubeadm join to connect a node to the cluster
  • kubeadm reset to revert any changes made to this host by kubeadm init or kubeadm join

10 - kubeadm certs

kubeadm certs provides utilities for managing certificates. For more details on how these commands can be used, see Certificate Management with kubeadm.

kubeadm certs

A collection of operations for operating Kubernetes certificates.

Commands related to handling kubernetes certificates

Synopsis

Commands related to handling kubernetes certificates

Options

-h, --help

help for certs

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm certs renew

You can renew all Kubernetes certificates using the all subcommand or renew them selectively. For more details see Manual certificate renewal.

Renew certificates for a Kubernetes cluster

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm certs renew [flags]

Options

-h, --help

help for renew

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew all available certificates

Synopsis

Renew all known certificates necessary to run the control plane. Renewals are run unconditionally, regardless of expiration date. Renewals can also be run individually for more control.

kubeadm certs renew all [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for all

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate embedded in the kubeconfig file for the admin to use and for kubeadm itself

Synopsis

Renew the certificate embedded in the kubeconfig file for the admin to use and for kubeadm itself.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew admin.conf [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for admin.conf

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate the apiserver uses to access etcd

Synopsis

Renew the certificate the apiserver uses to access etcd.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew apiserver-etcd-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for apiserver-etcd-client

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate for the API server to connect to kubelet

Synopsis

Renew the certificate for the API server to connect to kubelet.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew apiserver-kubelet-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for apiserver-kubelet-client

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate for serving the Kubernetes API

Synopsis

Renew the certificate for serving the Kubernetes API.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew apiserver [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for apiserver

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate embedded in the kubeconfig file for the controller manager to use

Synopsis

Renew the certificate embedded in the kubeconfig file for the controller manager to use.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew controller-manager.conf [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for controller-manager.conf

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate for liveness probes to healthcheck etcd

Synopsis

Renew the certificate for liveness probes to healthcheck etcd.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew etcd-healthcheck-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for etcd-healthcheck-client

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate for etcd nodes to communicate with each other

Synopsis

Renew the certificate for etcd nodes to communicate with each other.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew etcd-peer [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for etcd-peer

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate for serving etcd

Synopsis

Renew the certificate for serving etcd.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew etcd-server [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for etcd-server

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate for the front proxy client

Synopsis

Renew the certificate for the front proxy client.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew front-proxy-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for front-proxy-client

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Renew the certificate embedded in the kubeconfig file for the scheduler manager to use

Synopsis

Renew the certificate embedded in the kubeconfig file for the scheduler manager to use.

Renewals run unconditionally, regardless of certificate expiration date; extra attributes such as SANs will be based on the existing file/certificates, there is no need to resupply them.

Renewal by default tries to use the certificate authority in the local PKI managed by kubeadm; as alternative it is possible to use K8s certificate API for certificate renewal, or as a last option, to generate a CSR request.

After renewal, in order to make changes effective, is required to restart control-plane components and eventually re-distribute the renewed certificate in case the file is used elsewhere.

kubeadm certs renew scheduler.conf [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

--csr-dir string

The path to output the CSRs and private keys to

--csr-only

Create CSRs instead of generating certificates

-h, --help

help for scheduler.conf

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm certs certificate-key

This command can be used to generate a new control-plane certificate key. The key can be passed as --certificate-key to kubeadm init and kubeadm join to enable the automatic copy of certificates when joining additional control-plane nodes.

Generate certificate keys

Synopsis

This command will print out a secure randomly-generated certificate key that can be used with the "init" command.

You can also use "kubeadm init --upload-certs" without specifying a certificate key and it will generate and print one for you.

kubeadm certs certificate-key [flags]

Options

-h, --help

help for certificate-key

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm certs check-expiration

This command checks expiration for the certificates in the local PKI managed by kubeadm. For more details see Check certificate expiration.

Check certificates expiration for a Kubernetes cluster

Synopsis

Checks expiration for the certificates in the local PKI managed by kubeadm.

kubeadm certs check-expiration [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

-h, --help

help for check-expiration

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm certs generate-csr

This command can be used to generate keys and CSRs for all control-plane certificates and kubeconfig files. The user can then sign the CSRs with a CA of their choice.

Generate keys and certificate signing requests

Synopsis

Generates keys and certificate signing requests (CSRs) for all the certificates required to run the control plane. This command also generates partial kubeconfig files with private key data in the "users > user > client-key-data" field, and for each kubeconfig file an accompanying ".csr" file is created.

This command is designed for use in Kubeadm External CA Mode. It generates CSRs which you can then submit to your external certificate authority for signing.

The PEM encoded signed certificates should then be saved alongside the key files, using ".crt" as the file extension, or in the case of kubeconfig files, the PEM encoded signed certificate should be base64 encoded and added to the kubeconfig file in the "users > user > client-certificate-data" field.

kubeadm certs generate-csr [flags]

Examples

  # The following command will generate keys and CSRs for all control-plane certificates and kubeconfig files:
  kubeadm alpha certs generate-csr --kubeconfig-dir /tmp/etc-k8s --cert-dir /tmp/etc-k8s/pki

Options

--cert-dir string

The path where to save the certificates

--config string

Path to a kubeadm configuration file.

-h, --help

help for generate-csr

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

What's next

  • kubeadm init to bootstrap a Kubernetes control-plane node
  • kubeadm join to connect a node to the cluster
  • kubeadm reset to revert any changes made to this host by kubeadm init or kubeadm join

11 - kubeadm init phase

kubeadm init phase enables you to invoke atomic steps of the bootstrap process. Hence, you can let kubeadm do some of the work and you can fill in the gaps if you wish to apply customization.

kubeadm init phase is consistent with the kubeadm init workflow, and behind the scene both use the same code.

kubeadm init phase preflight

Using this command you can execute preflight checks on a control-plane node.

Run pre-flight checks

Synopsis

Run pre-flight checks for kubeadm init.

kubeadm init phase preflight [flags]

Examples

  # Run pre-flight checks for kubeadm init using a config file.
  kubeadm init phase preflight --config kubeadm-config.yaml

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for preflight

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase kubelet-start

This phase will write the kubelet configuration file and environment file and then start the kubelet.

Write kubelet settings and (re)start the kubelet

Synopsis

Write a file with KubeletConfiguration and an environment file with node specific kubelet settings, and then (re)start kubelet.

kubeadm init phase kubelet-start [flags]

Examples

  # Writes a dynamic environment file with kubelet flags from a InitConfiguration file.
  kubeadm init phase kubelet-start --config config.yaml

Options

--config string

Path to a kubeadm configuration file.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

-h, --help

help for kubelet-start

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase certs

Can be used to create all required certificates by kubeadm.

Certificate generation

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase certs [flags]

Options

-h, --help

help for certs

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate all certificates

Synopsis

Generate all certificates

kubeadm init phase certs all [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-cert-extra-sans strings

Optional extra Subject Alternative Names (SANs) to use for the API Server serving certificate. Can be both IP addresses and DNS names.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for all

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the self-signed Kubernetes CA to provision identities for other Kubernetes components

Synopsis

Generate the self-signed Kubernetes CA to provision identities for other Kubernetes components, and save them into ca.cert and ca.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs ca [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for ca

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the certificate for serving the Kubernetes API

Synopsis

Generate the certificate for serving the Kubernetes API, and save them into apiserver.cert and apiserver.key files.

Default SANs are kubernetes, kubernetes.default, kubernetes.default.svc, kubernetes.default.svc.cluster.local, 10.96.0.1, 127.0.0.1

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs apiserver [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-cert-extra-sans strings

Optional extra Subject Alternative Names (SANs) to use for the API Server serving certificate. Can be both IP addresses and DNS names.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for apiserver

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the certificate for the API server to connect to kubelet

Synopsis

Generate the certificate for the API server to connect to kubelet, and save them into apiserver-kubelet-client.cert and apiserver-kubelet-client.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs apiserver-kubelet-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for apiserver-kubelet-client

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the self-signed CA to provision identities for front proxy

Synopsis

Generate the self-signed CA to provision identities for front proxy, and save them into front-proxy-ca.cert and front-proxy-ca.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs front-proxy-ca [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for front-proxy-ca

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the certificate for the front proxy client

Synopsis

Generate the certificate for the front proxy client, and save them into front-proxy-client.cert and front-proxy-client.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs front-proxy-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for front-proxy-client

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the self-signed CA to provision identities for etcd

Synopsis

Generate the self-signed CA to provision identities for etcd, and save them into etcd/ca.cert and etcd/ca.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs etcd-ca [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for etcd-ca

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the certificate for serving etcd

Synopsis

Generate the certificate for serving etcd, and save them into etcd/server.cert and etcd/server.key files.

Default SANs are localhost, 127.0.0.1, 127.0.0.1, ::1

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs etcd-server [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for etcd-server

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the certificate for etcd nodes to communicate with each other

Synopsis

Generate the certificate for etcd nodes to communicate with each other, and save them into etcd/peer.cert and etcd/peer.key files.

Default SANs are localhost, 127.0.0.1, 127.0.0.1, ::1

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs etcd-peer [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for etcd-peer

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the certificate for liveness probes to healthcheck etcd

Synopsis

Generate the certificate for liveness probes to healthcheck etcd, and save them into etcd/healthcheck-client.cert and etcd/healthcheck-client.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs etcd-healthcheck-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for etcd-healthcheck-client

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the certificate the apiserver uses to access etcd

Synopsis

Generate the certificate the apiserver uses to access etcd, and save them into apiserver-etcd-client.cert and apiserver-etcd-client.key files.

If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs apiserver-etcd-client [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for apiserver-etcd-client

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate a private key for signing service account tokens along with its public key

Synopsis

Generate the private key for signing service account tokens along with its public key, and save them into sa.key and sa.pub files. If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

kubeadm init phase certs sa [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

-h, --help

help for sa

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase kubeconfig

You can create all required kubeconfig files by calling the all subcommand or call them individually.

Generate all kubeconfig files necessary to establish the control plane and the admin kubeconfig file

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase kubeconfig [flags]

Options

-h, --help

help for kubeconfig

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate all kubeconfig files

Synopsis

Generate all kubeconfig files

kubeadm init phase kubeconfig all [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for all

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate a kubeconfig file for the admin to use and for kubeadm itself

Synopsis

Generate the kubeconfig file for the admin and for kubeadm itself, and save it to admin.conf file.

kubeadm init phase kubeconfig admin [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for admin

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate a kubeconfig file for the kubelet to use only for cluster bootstrapping purposes

Synopsis

Generate the kubeconfig file for the kubelet to use and save it to kubelet.conf file.

Please note that this should only be used for cluster bootstrapping purposes. After your control plane is up, you should request all kubelet credentials from the CSR API.

kubeadm init phase kubeconfig kubelet [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for kubelet

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate a kubeconfig file for the controller manager to use

Synopsis

Generate the kubeconfig file for the controller manager to use and save it to controller-manager.conf file

kubeadm init phase kubeconfig controller-manager [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for controller-manager

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate a kubeconfig file for the scheduler to use

Synopsis

Generate the kubeconfig file for the scheduler to use and save it to scheduler.conf file.

kubeadm init phase kubeconfig scheduler [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for scheduler

--kubeconfig-dir string     Default: "/etc/kubernetes"

The path where to save the kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase control-plane

Using this phase you can create all required static Pod files for the control plane components.

Generate all static Pod manifest files necessary to establish the control plane

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase control-plane [flags]

Options

-h, --help

help for control-plane

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate all static Pod manifest files

Synopsis

Generate all static Pod manifest files

kubeadm init phase control-plane all [flags]

Examples

  # Generates all static Pod manifest files for control plane components,
  # functionally equivalent to what is generated by kubeadm init.
  kubeadm init phase control-plane all
  
  # Generates all static Pod manifest files using options read from a configuration file.
  kubeadm init phase control-plane all --config config.yaml

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--apiserver-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the API Server or override default ones in form of =

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

--controller-manager-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the Controller Manager or override default ones in form of =

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for all

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

--scheduler-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the Scheduler or override default ones in form of =

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generates the kube-apiserver static Pod manifest

Synopsis

Generates the kube-apiserver static Pod manifest

kubeadm init phase control-plane apiserver [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--apiserver-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the API Server or override default ones in form of =

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for apiserver

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generates the kube-controller-manager static Pod manifest

Synopsis

Generates the kube-controller-manager static Pod manifest

kubeadm init phase control-plane controller-manager [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--controller-manager-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the Controller Manager or override default ones in form of =

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for controller-manager

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generates the kube-scheduler static Pod manifest

Synopsis

Generates the kube-scheduler static Pod manifest

kubeadm init phase control-plane scheduler [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for scheduler

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--scheduler-extra-args <comma-separated 'key=value' pairs>

A set of extra flags to pass to the Scheduler or override default ones in form of =

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase etcd

Use the following phase to create a local etcd instance based on a static Pod file.

Generate static Pod manifest file for local etcd

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase etcd [flags]

Options

-h, --help

help for etcd

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the static Pod manifest file for a local, single-node local etcd instance

Synopsis

Generate the static Pod manifest file for a local, single-node local etcd instance

kubeadm init phase etcd local [flags]

Examples

  # Generates the static Pod manifest file for etcd, functionally
  # equivalent to what is generated by kubeadm init.
  kubeadm init phase etcd local
  
  # Generates the static Pod manifest file for etcd using options
  # read from a configuration file.
  kubeadm init phase etcd local --config config.yaml

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for local

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase upload-config

You can use this command to upload the kubeadm configuration to your cluster. Alternatively, you can use kubeadm config.

Upload the kubeadm and kubelet configuration to a ConfigMap

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase upload-config [flags]

Options

-h, --help

help for upload-config

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Upload all configuration to a config map

Synopsis

Upload all configuration to a config map

kubeadm init phase upload-config all [flags]

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for all

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Upload the kubeadm ClusterConfiguration to a ConfigMap

Synopsis

Upload the kubeadm ClusterConfiguration to a ConfigMap called kubeadm-config in the kube-system namespace. This enables correct configuration of system components and a seamless user experience when upgrading.

Alternatively, you can use kubeadm config.

kubeadm init phase upload-config kubeadm [flags]

Examples

  # upload the configuration of your cluster
  kubeadm init phase upload-config --config=myConfig.yaml

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for kubeadm

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Upload the kubelet component config to a ConfigMap

Synopsis

Upload kubelet configuration extracted from the kubeadm InitConfiguration object to a ConfigMap of the form kubelet-config-1.X in the cluster, where X is the minor version of the current (API Server) Kubernetes version.

kubeadm init phase upload-config kubelet [flags]

Examples

  # Upload the kubelet configuration from the kubeadm Config file to a ConfigMap in the cluster.
  kubeadm init phase upload-config kubelet --config kubeadm.yaml

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for kubelet

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase upload-certs

Use the following phase to upload control-plane certificates to the cluster. By default the certs and encryption key expire after two hours.

Upload certificates to kubeadm-certs

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase upload-certs [flags]

Options

--certificate-key string

Key used to encrypt the control-plane certificates in the kubeadm-certs Secret.

--config string

Path to a kubeadm configuration file.

-h, --help

help for upload-certs

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--skip-certificate-key-print

Don't print the key used to encrypt the control-plane certificates.

--upload-certs

Upload control-plane certificates to the kubeadm-certs Secret.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase mark-control-plane

Use the following phase to label and taint the node with the node-role.kubernetes.io/master="" key-value pair.

Mark a node as a control-plane

Synopsis

Mark a node as a control-plane

kubeadm init phase mark-control-plane [flags]

Examples

  # Applies control-plane label and taint to the current node, functionally equivalent to what executed by kubeadm init.
  kubeadm init phase mark-control-plane --config config.yaml
  
  # Applies control-plane label and taint to a specific node
  kubeadm init phase mark-control-plane --node-name myNode

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for mark-control-plane

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase bootstrap-token

Use the following phase to configure bootstrap tokens.

Generates bootstrap tokens used to join a node to a cluster

Synopsis

Bootstrap tokens are used for establishing bidirectional trust between a node joining the cluster and a control-plane node.

This command makes all the configurations required to make bootstrap tokens works and then creates an initial token.

kubeadm init phase bootstrap-token [flags]

Examples

  # Make all the bootstrap token configurations and create an initial token, functionally
  # equivalent to what generated by kubeadm init.
  kubeadm init phase bootstrap-token

Options

--config string

Path to a kubeadm configuration file.

-h, --help

help for bootstrap-token

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--skip-token-print

Skip printing of the default bootstrap token generated by 'kubeadm init'.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase kubelet-finialize

Use the following phase to update settings relevant to the kubelet after TLS bootstrap. You can use the all subcommand to run all kubelet-finalize phases.

Updates settings relevant to the kubelet after TLS bootstrap

Synopsis

Updates settings relevant to the kubelet after TLS bootstrap

kubeadm init phase kubelet-finalize [flags]

Examples

  # Updates settings relevant to the kubelet after TLS bootstrap"
  kubeadm init phase kubelet-finalize all --config

Options

-h, --help

help for kubelet-finalize

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Run all kubelet-finalize phases

Synopsis

Run all kubelet-finalize phases

kubeadm init phase kubelet-finalize all [flags]

Examples

  # Updates settings relevant to the kubelet after TLS bootstrap"
  kubeadm init phase kubelet-finalize all --config

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for all

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Enable kubelet client certificate rotation

Synopsis

Enable kubelet client certificate rotation

kubeadm init phase kubelet-finalize experimental-cert-rotation [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path where to save and store the certificates.

--config string

Path to a kubeadm configuration file.

-h, --help

help for experimental-cert-rotation

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm init phase addon

You can install all the available addons with the all subcommand, or install them selectively.

Install required addons for passing conformance tests

Synopsis

This command is not meant to be run on its own. See list of available subcommands.

kubeadm init phase addon [flags]

Options

-h, --help

help for addon

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Install all the addons

Synopsis

Install all the addons

kubeadm init phase addon all [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for all

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Install the CoreDNS addon to a Kubernetes cluster

Synopsis

Install the CoreDNS addon components via the API server. Please note that although the DNS server is deployed, it will not be scheduled until CNI is installed.

kubeadm init phase addon coredns [flags]

Options

--config string

Path to a kubeadm configuration file.

--feature-gates string

A set of key=value pairs that describe feature gates for various features. Options are:
IPv6DualStack=true|false (BETA - default=true)
PublicKeysECDSA=true|false (ALPHA - default=false)

-h, --help

help for coredns

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--service-cidr string     Default: "10.96.0.0/12"

Use alternative range of IP address for service VIPs.

--service-dns-domain string     Default: "cluster.local"

Use alternative domain for services, e.g. "myorg.internal".

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Install the kube-proxy addon to a Kubernetes cluster

Synopsis

Install the kube-proxy addon components via the API server.

kubeadm init phase addon kube-proxy [flags]

Options

--apiserver-advertise-address string

The IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

Port for the API Server to bind to.

--config string

Path to a kubeadm configuration file.

--control-plane-endpoint string

Specify a stable IP address or DNS name for the control plane.

-h, --help

help for kube-proxy

--image-repository string     Default: "k8s.gcr.io"

Choose a container registry to pull control plane images from

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

--kubernetes-version string     Default: "stable-1"

Choose a specific Kubernetes version for the control plane.

--pod-network-cidr string

Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

For more details on each field in the v1beta2 configuration you can navigate to our [API reference pages.] (https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2)

What's next

12 - kubeadm join phase

kubeadm join phase enables you to invoke atomic steps of the join process. Hence, you can let kubeadm do some of the work and you can fill in the gaps if you wish to apply customization.

kubeadm join phase is consistent with the kubeadm join workflow, and behind the scene both use the same code.

kubeadm join phase

Use this command to invoke single phase of the join workflow

Synopsis

Use this command to invoke single phase of the join workflow

Options

-h, --help

help for phase

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm join phase preflight

Using this phase you can execute preflight checks on a joining node.

Run join pre-flight checks

Synopsis

Run pre-flight checks for kubeadm join.

kubeadm join phase preflight [api-server-endpoint] [flags]

Examples

  # Run join pre-flight checks using a config file.
  kubeadm join phase preflight --config kubeadm-config.yaml

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

If the node should host a new control plane instance, the port for the API Server to bind to.

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for preflight

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

--node-name string

Specify the node name.

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm join phase control-plane-prepare

Using this phase you can prepare a node for serving a control-plane.

Prepare the machine for serving a control plane

Synopsis

Prepare the machine for serving a control plane

kubeadm join phase control-plane-prepare [flags]

Examples

  # Prepares the machine for serving a control plane
  kubeadm join phase control-plane-prepare all

Options

-h, --help

help for control-plane-prepare

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Prepare the machine for serving a control plane

Synopsis

Prepare the machine for serving a control plane

kubeadm join phase control-plane-prepare all [api-server-endpoint] [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

If the node should host a new control plane instance, the port for the API Server to bind to.

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for all

--node-name string

Specify the node name.

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

[EXPERIMENTAL] Download certificates shared among control-plane nodes from the kubeadm-certs Secret

Synopsis

[EXPERIMENTAL] Download certificates shared among control-plane nodes from the kubeadm-certs Secret

kubeadm join phase control-plane-prepare download-certs [api-server-endpoint] [flags]

Options

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for download-certs

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the certificates for the new control plane components

Synopsis

Generate the certificates for the new control plane components

kubeadm join phase control-plane-prepare certs [api-server-endpoint] [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for certs

--node-name string

Specify the node name.

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the kubeconfig for the new control plane components

Synopsis

Generate the kubeconfig for the new control plane components

kubeadm join phase control-plane-prepare kubeconfig [api-server-endpoint] [flags]

Options

--certificate-key string

Use this key to decrypt the certificate secrets uploaded by init.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for kubeconfig

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Generate the manifests for the new control plane components

Synopsis

Generate the manifests for the new control plane components

kubeadm join phase control-plane-prepare control-plane [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--apiserver-bind-port int32     Default: 6443

If the node should host a new control plane instance, the port for the API Server to bind to.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for control-plane

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm join phase kubelet-start

Using this phase you can write the kubelet settings, certificates and (re)start the kubelet.

Write kubelet settings, certificates and (re)start the kubelet

Synopsis

Write a file with KubeletConfiguration and an environment file with node specific kubelet settings, and then (re)start kubelet.

kubeadm join phase kubelet-start [api-server-endpoint] [flags]

Options

--config string

Path to kubeadm config file.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

--discovery-file string

For file-based discovery, a file or URL from which to load cluster information.

--discovery-token string

For token-based discovery, the token used to validate cluster information fetched from the API server.

--discovery-token-ca-cert-hash strings

For token-based discovery, validate that the root CA public key matches this hash (format: ":").

--discovery-token-unsafe-skip-ca-verification

For token-based discovery, allow joining without --discovery-token-ca-cert-hash pinning.

-h, --help

help for kubelet-start

--node-name string

Specify the node name.

--tls-bootstrap-token string

Specify the token used to temporarily authenticate with the Kubernetes Control Plane while joining the node.

--token string

Use this token for both discovery-token and tls-bootstrap-token when those values are not provided.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm join phase control-plane-join

Using this phase you can join a node as a control-plane instance.

Join a machine as a control plane instance

Synopsis

Join a machine as a control plane instance

kubeadm join phase control-plane-join [flags]

Examples

  # Joins a machine as a control plane instance
  kubeadm join phase control-plane-join all

Options

-h, --help

help for control-plane-join

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Join a machine as a control plane instance

Synopsis

Join a machine as a control plane instance

kubeadm join phase control-plane-join all [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

-h, --help

help for all

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Add a new local etcd member

Synopsis

Add a new local etcd member

kubeadm join phase control-plane-join etcd [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for etcd

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Register the new control-plane node into the ClusterStatus maintained in the kubeadm-config ConfigMap

Synopsis

Register the new control-plane node into the ClusterStatus maintained in the kubeadm-config ConfigMap

kubeadm join phase control-plane-join update-status [flags]

Options

--apiserver-advertise-address string

If the node should host a new control plane instance, the IP address the API Server will advertise it's listening on. If not set the default network interface will be used.

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

-h, --help

help for update-status

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Mark a node as a control-plane

Synopsis

Mark a node as a control-plane

kubeadm join phase control-plane-join mark-control-plane [flags]

Options

--config string

Path to kubeadm config file.

--control-plane

Create a new control plane instance on this node

-h, --help

help for mark-control-plane

--node-name string

Specify the node name.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

What's next

13 - kubeadm kubeconfig

kubeadm kubeconfig provides utilities for managing kubeconfig files.

kubeadm kubeconfig

Kubeconfig file utilities

Synopsis

Kubeconfig file utilities.

Alpha Disclaimer: this command is currently alpha.

Options

-h, --help

help for kubeconfig

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm kubeconfig user

This command can be used to output a kubeconfig file for an additional user.

Output a kubeconfig file for an additional user

Synopsis

Output a kubeconfig file for an additional user.

Alpha Disclaimer: this command is currently alpha.

kubeadm kubeconfig user [flags]

Examples

  # Output a kubeconfig file for an additional user named foo using a kubeadm config file bar
  kubeadm alpha kubeconfig user --client-name=foo --config=bar

Options

--client-name string

The name of user. It will be used as the CN if client certificates are created

--config string

Path to a kubeadm configuration file.

-h, --help

help for user

--org strings

The orgnizations of the client certificate. It will be used as the O if client certificates are created

--token string

The token that should be used as the authentication mechanism for this kubeconfig, instead of client certificates

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

14 - kubeadm reset phase

kubeadm reset phase enables you to invoke atomic steps of the node reset process. Hence, you can let kubeadm do some of the work and you can fill in the gaps if you wish to apply customization.

kubeadm reset phase is consistent with the kubeadm reset workflow, and behind the scene both use the same code.

kubeadm reset phase

Use this command to invoke single phase of the reset workflow

Synopsis

Use this command to invoke single phase of the reset workflow

Options

-h, --help

help for phase

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm reset phase preflight

Using this phase you can execute preflight checks on a node that is being reset.

Run reset pre-flight checks

Synopsis

Run pre-flight checks for kubeadm reset.

kubeadm reset phase preflight [flags]

Options

-f, --force

Reset the node without prompting for confirmation.

-h, --help

help for preflight

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm reset phase update-cluster-status

Using this phase you can remove this control-plane node from the ClusterStatus object.

Remove this node from the ClusterStatus object.

Synopsis

Remove this node from the ClusterStatus object if the node is a control plane node.

kubeadm reset phase update-cluster-status [flags]

Options

-h, --help

help for update-cluster-status

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm reset phase remove-etcd-member

Using this phase you can remove this control-plane node's etcd member from the etcd cluster.

Remove a local etcd member.

Synopsis

Remove a local etcd member for a control plane node.

kubeadm reset phase remove-etcd-member [flags]

Options

-h, --help

help for remove-etcd-member

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

kubeadm reset phase cleanup-node

Using this phase you can perform cleanup on this node.

Run cleanup node.

Synopsis

Run cleanup node.

kubeadm reset phase cleanup-node [flags]

Options

--cert-dir string     Default: "/etc/kubernetes/pki"

The path to the directory where the certificates are stored. If specified, clean this directory.

--cri-socket string

Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.

-h, --help

help for cleanup-node

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

What's next

15 - kubeadm upgrade phase

In v1.15.0, kubeadm introduced preliminary support for kubeadm upgrade node phases. Phases for other kubeadm upgrade sub-commands such as apply, could be added in the following releases.

kubeadm upgrade node phase

Using this phase you can choose to execute the separate steps of the upgrade of secondary control-plane or worker nodes. Please note that kubeadm upgrade apply still has to be called on a primary control-plane node.

Use this command to invoke single phase of the node workflow

Synopsis

Use this command to invoke single phase of the node workflow

Options

-h, --help

help for phase

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Run upgrade node pre-flight checks

Synopsis

Run pre-flight checks for kubeadm upgrade node.

kubeadm upgrade node phase preflight [flags]

Options

-h, --help

help for preflight

--ignore-preflight-errors strings

A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Upgrade the control plane instance deployed on this node, if any

Synopsis

Upgrade the control plane instance deployed on this node, if any

kubeadm upgrade node phase control-plane [flags]

Options

--certificate-renewal     Default: true

Perform the renewal of certificates used by component changed during upgrades.

--dry-run

Do not change any state, just output the actions that would be performed.

--etcd-upgrade     Default: true

Perform the upgrade of etcd.

--experimental-patches string

Path to a directory that contains files named "target[suffix][+patchtype].extension". For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats supported by kubectl. The default "patchtype" is "strategic". "extension" must be either "json" or "yaml". "suffix" is an optional string that can be used to determine which patches are applied first alpha-numerically.

-h, --help

help for control-plane

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

Upgrade the kubelet configuration for this node

Synopsis

Download the kubelet configuration from a ConfigMap of the form "kubelet-config-1.X" in the cluster, where X is the minor version of the kubelet. kubeadm uses the KuberneteVersion field in the kubeadm-config ConfigMap to determine what the desired kubelet version is.

kubeadm upgrade node phase kubelet-config [flags]

Options

--dry-run

Do not change any state, just output the actions that would be performed.

-h, --help

help for kubelet-config

--kubeconfig string     Default: "/etc/kubernetes/admin.conf"

The kubeconfig file to use when talking to the cluster. If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.

Options inherited from parent commands

--rootfs string

[EXPERIMENTAL] The path to the 'real' host root filesystem.

What's next

16 - Implementation details

FEATURE STATE: Kubernetes v1.10 [stable]

kubeadm init and kubeadm join together provides a nice user experience for creating a best-practice but bare Kubernetes cluster from scratch. However, it might not be obvious how kubeadm does that.

This document provides additional details on what happen under the hood, with the aim of sharing knowledge on Kubernetes cluster best practices.

Core design principles

The cluster that kubeadm init and kubeadm join set up should be:

  • Secure: It should adopt latest best-practices like:
    • enforcing RBAC
    • using the Node Authorizer
    • using secure communication between the control plane components
    • using secure communication between the API server and the kubelets
    • lock-down the kubelet API
    • locking down access to the API for system components like the kube-proxy and CoreDNS
    • locking down what a Bootstrap Token can access
  • User-friendly: The user should not have to run anything more than a couple of commands:
    • kubeadm init
    • export KUBECONFIG=/etc/kubernetes/admin.conf
    • kubectl apply -f <network-of-choice.yaml>
    • kubeadm join --token <token> <endpoint>:<port>
  • Extendable:
    • It should not favor any particular network provider. Configuring the cluster network is out-of-scope
    • It should provide the possibility to use a config file for customizing various parameters

Constants and well-known values and paths

In order to reduce complexity and to simplify development of higher level tools that build on top of kubeadm, it uses a limited set of constant values for well-known paths and file names.

The Kubernetes directory /etc/kubernetes is a constant in the application, since it is clearly the given path in a majority of cases, and the most intuitive location; other constants paths and file names are:

  • /etc/kubernetes/manifests as the path where kubelet should look for static Pod manifests. Names of static Pod manifests are:
    • etcd.yaml
    • kube-apiserver.yaml
    • kube-controller-manager.yaml
    • kube-scheduler.yaml
  • /etc/kubernetes/ as the path where kubeconfig files with identities for control plane components are stored. Names of kubeconfig files are:
    • kubelet.conf (bootstrap-kubelet.conf during TLS bootstrap)
    • controller-manager.conf
    • scheduler.conf
    • admin.conf for the cluster admin and kubeadm itself
  • Names of certificates and key files :
    • ca.crt, ca.key for the Kubernetes certificate authority
    • apiserver.crt, apiserver.key for the API server certificate
    • apiserver-kubelet-client.crt, apiserver-kubelet-client.key for the client certificate used by the API server to connect to the kubelets securely
    • sa.pub, sa.key for the key used by the controller manager when signing ServiceAccount
    • front-proxy-ca.crt, front-proxy-ca.key for the front proxy certificate authority
    • front-proxy-client.crt, front-proxy-client.key for the front proxy client

kubeadm init workflow internal design

The kubeadm init internal workflow consists of a sequence of atomic work tasks to perform, as described in kubeadm init.

The kubeadm init phase command allows users to invoke each task individually, and ultimately offers a reusable and composable API/toolbox that can be used by other Kubernetes bootstrap tools, by any IT automation tool or by an advanced user for creating custom clusters.

Preflight checks

Kubeadm executes a set of preflight checks before starting the init, with the aim to verify preconditions and avoid common cluster startup problems. The user can skip specific preflight checks or all of them with the --ignore-preflight-errors option.

  • [warning] If the Kubernetes version to use (specified with the --kubernetes-version flag) is at least one minor version higher than the kubeadm CLI version.
  • Kubernetes system requirements:
    • if running on linux:
      • [error] if Kernel is older than the minimum required version
      • [error] if required cgroups subsystem aren't in set up
    • if using docker:
      • [warning/error] if Docker service does not exist, if it is disabled, if it is not active.
      • [error] if Docker endpoint does not exist or does not work
      • [warning] if docker version is not in the list of validated docker versions
    • If using other cri engine:
      • [error] if crictl socket does not answer
  • [error] if user is not root
  • [error] if the machine hostname is not a valid DNS subdomain
  • [warning] if the host name cannot be reached via network lookup
  • [error] if kubelet version is lower that the minimum kubelet version supported by kubeadm (current minor -1)
  • [error] if kubelet version is at least one minor higher than the required controlplane version (unsupported version skew)
  • [warning] if kubelet service does not exist or if it is disabled
  • [warning] if firewalld is active
  • [error] if API server bindPort or ports 10250/10251/10252 are used
  • [Error] if /etc/kubernetes/manifest folder already exists and it is not empty
  • [Error] if /proc/sys/net/bridge/bridge-nf-call-iptables file does not exist/does not contain 1
  • [Error] if advertise address is ipv6 and /proc/sys/net/bridge/bridge-nf-call-ip6tables does not exist/does not contain 1.
  • [Error] if swap is on
  • [Error] if conntrack, ip, iptables, mount, nsenter commands are not present in the command path
  • [warning] if ebtables, ethtool, socat, tc, touch, crictl commands are not present in the command path
  • [warning] if extra arg flags for API server, controller manager, scheduler contains some invalid options
  • [warning] if connection to https://API.AdvertiseAddress:API.BindPort goes through proxy
  • [warning] if connection to services subnet goes through proxy (only first address checked)
  • [warning] if connection to Pods subnet goes through proxy (only first address checked)
  • If external etcd is provided:
    • [Error] if etcd version is older than the minimum required version
    • [Error] if etcd certificates or keys are specified, but not provided
  • If external etcd is NOT provided (and thus local etcd will be installed):
    • [Error] if ports 2379 is used
    • [Error] if Etcd.DataDir folder already exists and it is not empty
  • If authorization mode is ABAC:
    • [Error] if abac_policy.json does not exist
  • If authorization mode is WebHook
    • [Error] if webhook_authz.conf does not exist

Please note that:

  1. Preflight checks can be invoked individually with the kubeadm init phase preflight command

Generate the necessary certificates

Kubeadm generates certificate and private key pairs for different purposes:

  • A self signed certificate authority for the Kubernetes cluster saved into ca.crt file and ca.key private key file
  • A serving certificate for the API server, generated using ca.crt as the CA, and saved into apiserver.crt file with its private key apiserver.key. This certificate should contain following alternative names:
    • The Kubernetes service's internal clusterIP (the first address in the services CIDR, e.g. 10.96.0.1 if service subnet is 10.96.0.0/12)
    • Kubernetes DNS names, e.g. kubernetes.default.svc.cluster.local if --service-dns-domain flag value is cluster.local, plus default DNS names kubernetes.default.svc, kubernetes.default, kubernetes
    • The node-name
    • The --apiserver-advertise-address
    • Additional alternative names specified by the user
  • A client certificate for the API server to connect to the kubelets securely, generated using ca.crt as the CA and saved into apiserver-kubelet-client.crt file with its private key apiserver-kubelet-client.key. This certificate should be in the system:masters organization
  • A private key for signing ServiceAccount Tokens saved into sa.key file along with its public key sa.pub
  • A certificate authority for the front proxy saved into front-proxy-ca.crt file with its key front-proxy-ca.key
  • A client cert for the front proxy client, generate using front-proxy-ca.crt as the CA and saved into front-proxy-client.crt file with its private keyfront-proxy-client.key

Certificates are stored by default in /etc/kubernetes/pki, but this directory is configurable using the --cert-dir flag.

Please note that:

  1. If a given certificate and private key pair both exist, and its content is evaluated compliant with the above specs, the existing files will be used and the generation phase for the given certificate skipped. This means the user can, for example, copy an existing CA to /etc/kubernetes/pki/ca.{crt,key}, and then kubeadm will use those files for signing the rest of the certs. See also using custom certificates
  2. Only for the CA, it is possible to provide the ca.crt file but not the ca.key file, if all other certificates and kubeconfig files already are in place kubeadm recognize this condition and activates the ExternalCA , which also implies the csrsignercontroller in controller-manager won't be started
  3. If kubeadm is running in external CA mode; all the certificates must be provided by the user, because kubeadm cannot generate them by itself
  4. In case of kubeadm is executed in the --dry-run mode, certificates files are written in a temporary folder
  5. Certificate generation can be invoked individually with the kubeadm init phase certs all command

Generate kubeconfig files for control plane components

Kubeadm generates kubeconfig files with identities for control plane components:

  • A kubeconfig file for the kubelet to use during TLS bootstrap - /etc/kubernetes/bootstrap-kubelet.conf. Inside this file there is a bootstrap-token or embedded client certificates for authenticating this node with the cluster. This client cert should:
    • Be in the system:nodes organization, as required by the Node Authorization module
    • Have the Common Name (CN) system:node:<hostname-lowercased>
  • A kubeconfig file for controller-manager, /etc/kubernetes/controller-manager.conf; inside this file is embedded a client certificate with controller-manager identity. This client cert should have the CN system:kube-controller-manager, as defined by default RBAC core components roles
  • A kubeconfig file for scheduler, /etc/kubernetes/scheduler.conf; inside this file is embedded a client certificate with scheduler identity. This client cert should have the CN system:kube-scheduler, as defined by default RBAC core components roles

Additionally, a kubeconfig file for kubeadm itself and the admin is generated and saved into the /etc/kubernetes/admin.conf file. The "admin" here is defined as the actual person(s) that is administering the cluster and wants to have full control (root) over the cluster. The embedded client certificate for admin should be in the system:masters organization, as defined by default RBAC user facing role bindings. It should also include a CN. Kubeadm uses the kubernetes-admin CN.

Please note that:

  1. ca.crt certificate is embedded in all the kubeconfig files.
  2. If a given kubeconfig file exists, and its content is evaluated compliant with the above specs, the existing file will be used and the generation phase for the given kubeconfig skipped
  3. If kubeadm is running in ExternalCA mode, all the required kubeconfig must be provided by the user as well, because kubeadm cannot generate any of them by itself
  4. In case of kubeadm is executed in the --dry-run mode, kubeconfig files are written in a temporary folder
  5. Kubeconfig files generation can be invoked individually with the kubeadm init phase kubeconfig all command

Generate static Pod manifests for control plane components

Kubeadm writes static Pod manifest files for control plane components to /etc/kubernetes/manifests. The kubelet watches this directory for Pods to create on startup.

Static Pod manifest share a set of common properties:

  • All static Pods are deployed on kube-system namespace
  • All static Pods get tier:control-plane and component:{component-name} labels
  • All static Pods use the system-node-critical priority class
  • hostNetwork: true is set on all static Pods to allow control plane startup before a network is configured; as a consequence:
    • The address that the controller-manager and the scheduler use to refer the API server is 127.0.0.1
    • If using a local etcd server, etcd-servers address will be set to 127.0.0.1:2379
  • Leader election is enabled for both the controller-manager and the scheduler
  • Controller-manager and the scheduler will reference kubeconfig files with their respective, unique identities
  • All static Pods get any extra flags specified by the user as described in passing custom arguments to control plane components
  • All static Pods get any extra Volumes specified by the user (Host path)

Please note that:

  1. All images will be pulled from k8s.gcr.io by default. See using custom images for customizing the image repository
  2. In case of kubeadm is executed in the --dry-run mode, static Pods files are written in a temporary folder
  3. Static Pod manifest generation for control plane components can be invoked individually with the kubeadm init phase control-plane all command

API server

The static Pod manifest for the API server is affected by following parameters provided by the users:

  • The apiserver-advertise-address and apiserver-bind-port to bind to; if not provided, those value defaults to the IP address of the default network interface on the machine and port 6443
  • The service-cluster-ip-range to use for services
  • If an external etcd server is specified, the etcd-servers address and related TLS settings (etcd-cafile, etcd-certfile, etcd-keyfile); if an external etcd server is not be provided, a local etcd will be used (via host network)
  • If a cloud provider is specified, the corresponding --cloud-provider is configured, together with the --cloud-config path if such file exists (this is experimental, alpha and will be removed in a future version)

Other API server flags that are set unconditionally are:

  • --insecure-port=0 to avoid insecure connections to the api server
  • --enable-bootstrap-token-auth=true to enable the BootstrapTokenAuthenticator authentication module. See TLS Bootstrapping for more details
  • --allow-privileged to true (required e.g. by kube proxy)
  • --requestheader-client-ca-file to front-proxy-ca.crt
  • --enable-admission-plugins to:
    • NamespaceLifecycle e.g. to avoid deletion of system reserved namespaces
    • LimitRanger and ResourceQuota to enforce limits on namespaces
    • ServiceAccount to enforce service account automation
    • PersistentVolumeLabel attaches region or zone labels to PersistentVolumes as defined by the cloud provider (This admission controller is deprecated and will be removed in a future version. It is not deployed by kubeadm by default with v1.9 onwards when not explicitly opting into using gce or aws as cloud providers)
    • DefaultStorageClass to enforce default storage class on PersistentVolumeClaim objects
    • DefaultTolerationSeconds
    • NodeRestriction to limit what a kubelet can modify (e.g. only pods on this node)
  • --kubelet-preferred-address-types to InternalIP,ExternalIP,Hostname; this makes kubectl logs and other API server-kubelet communication work in environments where the hostnames of the nodes aren't resolvable
  • Flags for using certificates generated in previous steps:
    • --client-ca-file to ca.crt
    • --tls-cert-file to apiserver.crt
    • --tls-private-key-file to apiserver.key
    • --kubelet-client-certificate to apiserver-kubelet-client.crt
    • --kubelet-client-key to apiserver-kubelet-client.key
    • --service-account-key-file to sa.pub
    • --requestheader-client-ca-file tofront-proxy-ca.crt
    • --proxy-client-cert-file to front-proxy-client.crt
    • --proxy-client-key-file to front-proxy-client.key
  • Other flags for securing the front proxy (API Aggregation) communications:
    • --requestheader-username-headers=X-Remote-User
    • --requestheader-group-headers=X-Remote-Group
    • --requestheader-extra-headers-prefix=X-Remote-Extra-
    • --requestheader-allowed-names=front-proxy-client

Controller manager

The static Pod manifest for the API server is affected by following parameters provided by the users:

  • If kubeadm is invoked specifying a --pod-network-cidr, the subnet manager feature required for some CNI network plugins is enabled by setting:
    • --allocate-node-cidrs=true
    • --cluster-cidr and --node-cidr-mask-size flags according to the given CIDR
  • If a cloud provider is specified, the corresponding --cloud-provider is specified, together with the --cloud-config path if such configuration file exists (this is experimental, alpha and will be removed in a future version)

Other flags that are set unconditionally are:

  • --controllers enabling all the default controllers plus BootstrapSigner and TokenCleaner controllers for TLS bootstrap. See TLS Bootstrapping for more details
  • --use-service-account-credentials to true
  • Flags for using certificates generated in previous steps:
    • --root-ca-file to ca.crt
    • --cluster-signing-cert-file to ca.crt, if External CA mode is disabled, otherwise to ""
    • --cluster-signing-key-file to ca.key, if External CA mode is disabled, otherwise to ""
    • --service-account-private-key-file to sa.key

Scheduler

The static Pod manifest for the scheduler is not affected by parameters provided by the users.

Generate static Pod manifest for local etcd

If the user specified an external etcd this step will be skipped, otherwise kubeadm generates a static Pod manifest file for creating a local etcd instance running in a Pod with following attributes:

  • listen on localhost:2379 and use HostNetwork=true
  • make a hostPath mount out from the dataDir to the host's filesystem
  • Any extra flags specified by the user

Please note that:

  1. The etcd image will be pulled from k8s.gcr.io by default. See using custom images for customizing the image repository
  2. in case of kubeadm is executed in the --dry-run mode, the etcd static Pod manifest is written in a temporary folder
  3. Static Pod manifest generation for local etcd can be invoked individually with the kubeadm init phase etcd local command

Optional Dynamic Kubelet Configuration

To use this functionality call kubeadm alpha kubelet config enable-dynamic. It writes the kubelet init configuration into /var/lib/kubelet/config/init/kubelet file.

The init configuration is used for starting the kubelet on this specific node, providing an alternative for the kubelet drop-in file; such configuration will be replaced by the kubelet base configuration as described in following steps. See set kubelet parameters via a config file for additional information.

Please note that:

  1. To make dynamic kubelet configuration work, flag --dynamic-config-dir=/var/lib/kubelet/config/dynamic should be specified in /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
  2. The kubelet configuration can be changed by passing a KubeletConfiguration object to kubeadm init or kubeadm join by using a configuration file --config some-file.yaml. The KubeletConfiguration object can be separated from other objects such as InitConfiguration using the --- separator. For more details have a look at the kubeadm config print-default command.

For more details about the KubeletConfiguration struct, take a look at the KubeletConfiguration reference.

Wait for the control plane to come up

kubeadm waits (upto 4m0s) until localhost:6443/healthz (kube-apiserver liveness) returns ok. However in order to detect deadlock conditions, kubeadm fails fast if localhost:10255/healthz (kubelet liveness) or localhost:10255/healthz/syncloop (kubelet readiness) don't return ok within 40s and 60s respectively.

kubeadm relies on the kubelet to pull the control plane images and run them properly as static Pods. After the control plane is up, kubeadm completes the tasks described in following paragraphs.

(optional) Write base kubelet configuration

FEATURE STATE: Kubernetes v1.11 [beta]

If kubeadm is invoked with --feature-gates=DynamicKubeletConfig:

  1. Write the kubelet base configuration into the kubelet-base-config-v1.9 ConfigMap in the kube-system namespace
  2. Creates RBAC rules for granting read access to that ConfigMap to all bootstrap tokens and all kubelet instances (that is system:bootstrappers:kubeadm:default-node-token and system:nodes groups)
  3. Enable the dynamic kubelet configuration feature for the initial control-plane node by pointing Node.spec.configSource to the newly-created ConfigMap

Save the kubeadm ClusterConfiguration in a ConfigMap for later reference

kubeadm saves the configuration passed to kubeadm init in a ConfigMap named kubeadm-config under kube-system namespace.

This will ensure that kubeadm actions executed in future (e.g kubeadm upgrade) will be able to determine the actual/current cluster state and make new decisions based on that data.

Please note that:

  1. Before saving the ClusterConfiguration, sensitive information like the token is stripped from the configuration
  2. Upload of control plane node configuration can be invoked individually with the kubeadm init phase upload-config command

Mark the node as control-plane

As soon as the control plane is available, kubeadm executes following actions:

  • Labels the node as control-plane with node-role.kubernetes.io/master=""
  • Taints the node with node-role.kubernetes.io/master:NoSchedule

Please note that:

  1. Mark control-plane phase phase can be invoked individually with the kubeadm init phase mark-control-plane command

Configure TLS-Bootstrapping for node joining

Kubeadm uses Authenticating with Bootstrap Tokens for joining new nodes to an existing cluster; for more details see also design proposal.

kubeadm init ensures that everything is properly configured for this process, and this includes following steps as well as setting API server and controller flags as already described in previous paragraphs. Please note that:

  1. TLS bootstrapping for nodes can be configured with the kubeadm init phase bootstrap-token command, executing all the configuration steps described in following paragraphs; alternatively, each step can be invoked individually

Create a bootstrap token

kubeadm init create a first bootstrap token, either generated automatically or provided by the user with the --token flag; as documented in bootstrap token specification, token should be saved as secrets with name bootstrap-token-<token-id> under kube-system namespace. Please note that:

  1. The default token created by kubeadm init will be used to validate temporary user during TLS bootstrap process; those users will be member of system:bootstrappers:kubeadm:default-node-token group
  2. The token has a limited validity, default 24 hours (the interval may be changed with the —token-ttl flag)
  3. Additional tokens can be created with the kubeadm token command, that provide as well other useful functions for token management

Allow joining nodes to call CSR API

Kubeadm ensures that users in system:bootstrappers:kubeadm:default-node-token group are able to access the certificate signing API.

This is implemented by creating a ClusterRoleBinding named kubeadm:kubelet-bootstrap between the group above and the default RBAC role system:node-bootstrapper.

Setup auto approval for new bootstrap tokens

Kubeadm ensures that the Bootstrap Token will get its CSR request automatically approved by the csrapprover controller.

This is implemented by creating ClusterRoleBinding named kubeadm:node-autoapprove-bootstrap between the system:bootstrappers:kubeadm:default-node-token group and the default role system:certificates.k8s.io:certificatesigningrequests:nodeclient.

The role system:certificates.k8s.io:certificatesigningrequests:nodeclient should be created as well, granting POST permission to /apis/certificates.k8s.io/certificatesigningrequests/nodeclient.

Setup nodes certificate rotation with auto approval

Kubeadm ensures that certificate rotation is enabled for nodes, and that new certificate request for nodes will get its CSR request automatically approved by the csrapprover controller.

This is implemented by creating ClusterRoleBinding named kubeadm:node-autoapprove-certificate-rotation between the system:nodes group and the default role system:certificates.k8s.io:certificatesigningrequests:selfnodeclient.

Create the public cluster-info ConfigMap

This phase creates the cluster-info ConfigMap in the kube-public namespace.

Additionally it creates a Role and a RoleBinding granting access to the ConfigMap for unauthenticated users (i.e. users in RBAC group system:unauthenticated).

Please note that:

  1. The access to the cluster-info ConfigMap is not rate-limited. This may or may not be a problem if you expose your cluster's API server to the internet; worst-case scenario here is a DoS attack where an attacker uses all the in-flight requests the kube-apiserver can handle to serving the cluster-info ConfigMap.

Install addons

Kubeadm installs the internal DNS server and the kube-proxy addon components via the API server. Please note that:

  1. This phase can be invoked individually with the kubeadm init phase addon all command.

proxy

A ServiceAccount for kube-proxy is created in the kube-system namespace; then kube-proxy is deployed as a DaemonSet:

  • The credentials (ca.crt and token) to the control plane come from the ServiceAccount
  • The location (URL) of the API server comes from a ConfigMap
  • The kube-proxy ServiceAccount is bound to the privileges in the system:node-proxier ClusterRole

DNS

  • The CoreDNS service is named kube-dns. This is done to prevent any interruption in service when the user is switching the cluster DNS from kube-dns to CoreDNS the --config method described here.
  • A ServiceAccount for CoreDNS is created in the kube-system namespace.
  • The coredns ServiceAccount is bound to the privileges in the system:coredns ClusterRole

In Kubernetes version 1.21, support for using kube-dns with kubeadm was removed. You can use CoreDNS with kubeadm even when the related Service is named kube-dns.

kubeadm join phases internal design

Similarly to kubeadm init, also kubeadm join internal workflow consists of a sequence of atomic work tasks to perform.

This is split into discovery (having the Node trust the Kubernetes Master) and TLS bootstrap (having the Kubernetes Master trust the Node).

see Authenticating with Bootstrap Tokens or the corresponding design proposal.

Preflight checks

kubeadm executes a set of preflight checks before starting the join, with the aim to verify preconditions and avoid common cluster startup problems.

Please note that:

  1. kubeadm join preflight checks are basically a subset kubeadm init preflight checks
  2. Starting from 1.9, kubeadm provides better support for CRI-generic functionality; in that case, docker specific controls are skipped or replaced by similar controls for crictl.
  3. Starting from 1.9, kubeadm provides support for joining nodes running on Windows; in that case, linux specific controls are skipped.
  4. In any case the user can skip specific preflight checks (or eventually all preflight checks) with the --ignore-preflight-errors option.

Discovery cluster-info

There are 2 main schemes for discovery. The first is to use a shared token along with the IP address of the API server. The second is to provide a file (that is a subset of the standard kubeconfig file).

Shared token discovery

If kubeadm join is invoked with --discovery-token, token discovery is used; in this case the node basically retrieves the cluster CA certificates from the cluster-info ConfigMap in the kube-public namespace.

In order to prevent "man in the middle" attacks, several steps are taken:

  • First, the CA certificate is retrieved via insecure connection (this is possible because kubeadm init granted access to cluster-info users for system:unauthenticated )
  • Then the CA certificate goes trough following validation steps:
    • Basic validation: using the token ID against a JWT signature
    • Pub key validation: using provided --discovery-token-ca-cert-hash. This value is available in the output of kubeadm init or can be calculated using standard tools (the hash is calculated over the bytes of the Subject Public Key Info (SPKI) object as in RFC7469). The --discovery-token-ca-cert-hash flag may be repeated multiple times to allow more than one public key.
    • As a additional validation, the CA certificate is retrieved via secure connection and then compared with the CA retrieved initially

Please note that:

  1. Pub key validation can be skipped passing --discovery-token-unsafe-skip-ca-verification flag; This weakens the kubeadm security model since others can potentially impersonate the Kubernetes Master.

File/https discovery

If kubeadm join is invoked with --discovery-file, file discovery is used; this file can be a local file or downloaded via an HTTPS URL; in case of HTTPS, the host installed CA bundle is used to verify the connection.

With file discovery, the cluster CA certificates is provided into the file itself; in fact, the discovery file is a kubeconfig file with only server and certificate-authority-data attributes set, as described in kubeadm join reference doc; when the connection with the cluster is established, kubeadm try to access the cluster-info ConfigMap, and if available, uses it.

TLS Bootstrap

Once the cluster info are known, the file bootstrap-kubelet.conf is written, thus allowing kubelet to do TLS Bootstrapping.

The TLS bootstrap mechanism uses the shared token to temporarily authenticate with the Kubernetes API server to submit a certificate signing request (CSR) for a locally created key pair.

The request is then automatically approved and the operation completes saving ca.crt file and kubelet.conf file to be used by kubelet for joining the cluster, whilebootstrap-kubelet.conf is deleted.

Please note that:

  • The temporary authentication is validated against the token saved during the kubeadm init process (or with additional tokens created with kubeadm token)
  • The temporary authentication resolve to a user member of system:bootstrappers:kubeadm:default-node-token group which was granted access to CSR api during the kubeadm init process
  • The automatic CSR approval is managed by the csrapprover controller, according with configuration done the kubeadm init process

(optional) Write init kubelet configuration

FEATURE STATE: Kubernetes v1.11 [beta]

If kubeadm is invoked with --feature-gates=DynamicKubeletConfig:

  1. Read the kubelet base configuration from the kubelet-base-config-v1.x ConfigMap in the kube-system namespace using the Bootstrap Token credentials, and write it to disk as kubelet init configuration file /var/lib/kubelet/config/init/kubelet
  2. As soon as kubelet starts with the Node's own credential (/etc/kubernetes/kubelet.conf), update current node configuration specifying that the source for the node/kubelet configuration is the above ConfigMap.

Please note that:

  1. To make dynamic kubelet configuration work, flag --dynamic-config-dir=/var/lib/kubelet/config/dynamic should be specified in /etc/systemd/system/kubelet.service.d/10-kubeadm.conf