Kubernetes version 1.5 includes a new command line tool called
kubefed to help you administrate your federated clusters.
kubefed helps you to deploy a new Kubernetes cluster federation
control plane, and to add clusters to or remove clusters from an
existing federation control plane.
This guide explains how to administer a Kubernetes Cluster Federation
kubefedis an alpha feature in Kubernetes 1.5.
This guide assumes that you have a running Kubernetes cluster. Please see one of the getting started guides for installation instructions for your platform.
Download the client tarball corresponding to Kubernetes version 1.5
from the release page,
extract the binaries in the tarball to one of the directories
$PATH and set the executable permission on those binaries.
curl -O https://storage.googleapis.com/kubernetes-release/release/v1.5.0/kubernetes-client-linux-amd64.tar.gz tar -xzvf kubernetes-client-linux-amd64.tar.gz sudo cp kubernetes/client/bin/kubefed /usr/local/bin sudo chmod +x /usr/local/bin/kubefed sudo cp kubernetes/client/bin/kubectl /usr/local/bin sudo chmod +x /usr/local/bin/kubectl
You’ll need to choose one of your Kubernetes clusters to be the
host cluster. The host cluster hosts the components that make up
your federation control plane. Ensure that you have a
entry in your local
kubeconfig that corresponds to the host cluster.
You can verify that you have the required
kubeconfig entry by
kubectl config get-contexts
The output should contain an entry corresponding to your host cluster, similar to the following:
CURRENT NAME CLUSTER AUTHINFO NAMESPACE gke_myproject_asia-east1-b_gce-asia-east1 gke_myproject_asia-east1-b_gce-asia-east1 gke_myproject_asia-east1-b_gce-asia-east1
You’ll need to provide the
kubeconfig context (called name in the
entry above) for your host cluster when you deploy your federation
“To deploy a federation control plane on your host cluster, run
kubefed init command. When you use
kubefed init, you must provide
kubeconfigcontext for the host cluster
--dns-zone-name, a domain name suffix for your federated services
The following example command deploys a federation control plane with
fellowship, a host cluster context
rivendell, and the
kubefed init fellowship --host-cluster-context=rivendell --dns-zone-name="example.com"
The domain suffix you specify in
--dns-zone-name must be an existing
domain that you control, and that is programmable by your DNS provider.
kubefed init sets up the federation control plane in the host
cluster and also adds an entry for the federation API server in your
local kubeconfig. Note that in the alpha release in Kubernetes 1.5,
kubefed init does not automatically set the current context to the
newly deployed federation. You can set the current context manually by
kubectl config use-context fellowship
fellowship is the name of your federation.
Once you’ve deployed a federation control plane, you’ll need to make
that control plane aware of the clusters it should manage. You can add
a cluster to your federation by using the
kubefed join command.
kubefed join, you’ll need to provide the name of the cluster
you want to add to the federation, and the
for the federation control plane’s host cluster.
The following example command adds the cluster
gondor to the
federation with host cluster
kubefed join gondor --host-cluster-context=rivendell
Note: Kubernetes requires that you manually join clusters to a federation because the federation control plane manages only those clusters that it is responsible for managing. Adding a cluster tells the federation control plane that it is responsible for managing that cluster.
The cluster name you supply to
kubefed join must be a valid RFC 1035
Furthermore, federation control plane requires credentials of the
joined clusters to operate on them. These credentials are obtained
from the local kubeconfig.
kubefed join uses the cluster name
specified as the argument to look for the cluster’s context in the
local kubeconfig. If it fails to find a matching context, it exits
with an error.
This might cause issues in cases where context names for each cluster
in the federation don’t follow RFC 1035 label naming rules. In such
cases, you can specify a cluster name that conforms to the RFC 1035
label naming rules and specify the cluster context using the
--cluster-context flag. For example, if context of the cluster your
are joining is
gondor_needs-no_king, then you can
join the cluster by running:
kubefed join gondor --host-cluster-context=rivendell --cluster-context=gondor_needs-no_king
Cluster credentials required by the federation control plane as described above are stored as a secret in the host cluster. The name of the secret is also derived from the cluster name.
However, the name of a secret object in Kubernetes should conform
to the subdomain name specification described in RFC 1123. If this
isn’t case, you can pass the secret name to
kubefed join using the
--secret-name flag. For example, if the cluster name is
the secret name is
11kingdom, you can join the cluster by
kubefed join noldor --host-cluster-context=rivendell --secret-name=11kingdom
To remove a cluster from a federation, run the
command with the cluster name and the federation’s
kubefed unjoin gondor --host-cluster-context=rivendell
Proper cleanup of federation control plane is not fully implemented in
this alpha release of
kubefed. However, for the time being, deleting
the federation system namespace should remove all the resources except
the persistent storage volume dynamically provisioned for the
federation control plane’s etcd. You can delete the federation
namespace by running the following command:
$ kubectl delete ns federation-system