Click on the [+] 特定の用語の詳細な説明を取得するには、以下のインジケータを使用します。
- Admission ControllerLINK
A piece of code that intercepts requests to the Kubernetes API server prior to persistence of the object.[+]
Admission controllers are configurable for the Kubernetes API server and may be "validating", "mutating", or both. Any admission controller may reject the request. Mutating controllers may modify the objects they admit; validating controllers may not.
In Kubernetes, affinity is a set of rules that give hints to the scheduler about where to place pods.[+]
- API GroupLINK
A set of related paths in Kubernetes API.[+]
You can enable or disable each API group by changing the configuration of your API server. You can also disable or enable paths to specific resources. API group makes it easier to extend the Kubernetes API. The API group is specified in a REST path and in the
apiVersionfield of a serialized object.
- Read API Group for more information.
APIサーバーは、Kubernetes APIを外部に提供するKubernetesコントロールプレーンのコンポーネントです。 APIサーバーはKubernetesコントロールプレーンのフロントエンドになります。[+]
Kubernetes APIサーバーの主な実装はkube-apiserverです。 kube-apiserverは水平方向にスケールするように設計されています—つまり、インスタンスを追加することでスケールが可能です。 複数のkube-apiserverインスタンスを実行することで、インスタンス間でトラフィックを分散させることが可能です。
- App ContainerLINK[+]
An init container lets you separate initialization details that are important for the overall workload, and that don't need to keep running once the application container has started. If a pod doesn't have any init containers configured, all the containers in that pod are app containers.
- Application ArchitectLINK
A person responsible for the high-level design of an application.[+]
An architect ensures that an app's implementation allows it to interact with its surrounding components in a scalable, maintainable way. Surrounding components include databases, logging infrastructure, and other microservices.
A person who can review and approve Kubernetes code contributions.[+]
While code review is focused on code quality and correctness, approval is focused on the holistic acceptance of a contribution. Holistic acceptance includes backwards/forwards compatibility, adhering to API and flag conventions, subtle performance and correctness issues, interactions with other parts of the system, and others. Approver status is scoped to a part of the codebase. Approvers were previously referred to as maintainers.
cAdvisor (Container Advisor) provides container users an understanding of the resource usage and performance characteristics of their running containers.[+]
It is a running daemon that collects, aggregates, processes, and exports information about running containers. Specifically, for each container it keeps resource isolation parameters, historical resource usage, histograms of complete historical resource usage and network statistics. This data is exported by container and machine-wide.
CIDR (Classless Inter-Domain Routing) is a notation for describing blocks of IP addresses and is used heavily in various networking configurations.[+]
- Cloud ProviderLINKまたの名を:Cloud Service Provider
A business or other organization that offers a cloud computing platform.[+]
Cloud providers, sometimes called Cloud Service Providers (CSPs), offer cloud computing platforms or services.
Many cloud providers offer managed infrastructure (also called Infrastructure as a Service or IaaS). With managed infrastructure the cloud provider is responsible for servers, storage, and networking while you manage layers on top of that such as running a Kubernetes cluster.
You can also find Kubernetes as a managed service; sometimes called Platform as a Service, or PaaS. With managed Kubernetes, your cloud provider is responsible for the Kubernetes control plane as well as the nodes and the infrastructure they rely on: networking, storage, and possibly other elements such as load balancers.
- Cluster OperationsLINK
The work involved in managing a Kubernetes cluster: managing day-to-day operations, and co-ordinating upgrades.[+]
Examples of cluster operations work include: deploying new Nodes to scale the cluster; performing software upgrades; implementing security controls; adding or removing storage; configuring cluster networking; managing cluster-wide observability; and responding to events.
- Container Environment VariablesLINK
Container environment variables are name=value pairs that provide useful information into containers running in a pod[+]
Container environment variables provide information that is required by the running containerized applications along with information about important resources to the containers. For example, file system details, information about the container itself, and other cluster resources such as service endpoints.
- Container Lifecycle HooksLINK
The lifecycle hooks expose events in the Container management lifecycle and let the user run code when the events occur.[+]
Two hooks are exposed to Containers: PostStart which executes immediately after a container is created and PreStop which is blocking and is called immediately before a container is terminated.
A tool that lets you use OCI container runtimes with Kubernetes CRI.[+]
Deploying CRI-O allows Kubernetes to use any OCI-compliant runtime as the container runtime for running Pods, and to fetch OCI container images from remote registries.
- Device PluginLINK[+]
Device plugins advertise resources to the kubelet, so that workload Pods can access hardware features that relate to the Node where that Pod is running. You can deploy a device plugin as a DaemonSet, or install the device plugin software directly on each target Node.
See Device Plugins for more information.
If you, as cluster operator, destroy a Pod that belongs to an application, Kubernetes terms that a voluntary disruption. If a Pod goes offline because of a Node failure, or an outage affecting a wider failure zone, Kubernetes terms that an involuntary disruption.
See Disruptions for more information.
- Downstream (disambiguation)LINK
May refer to: code in the Kubernetes ecosystem that depends upon the core Kubernetes codebase or a forked repo.[+]
- In the Kubernetes Community: Conversations often use downstream to mean the ecosystem, code, or third-party tools that rely on the core Kubernetes codebase. For example, a new feature in Kubernetes may be adopted by applications downstream to improve their functionality.
- In GitHub or git: The convention is to refer to a forked repo as downstream, whereas the source repo is considered upstream.
- Downward APILINK
Kubernetes' mechanism to expose Pod and container field values to code running in a container.[+]
It is sometimes useful for a container to have information about itself, without needing to make changes to the container code that directly couple it to Kubernetes.
The Kubernetes downward API allows containers to consume information about themselves or their context in a Kubernetes cluster. Applications in containers can have access to that information, without the application needing to act as a client of the Kubernetes API.
There are two ways to expose Pod and container fields to a running container:
Together, these two ways of exposing Pod and container fields are called the downward API.
- Dynamic Volume ProvisioningLINK
Allows users to request automatic creation of storage Volumes.[+]
Dynamic provisioning eliminates the need for cluster administrators to pre-provision storage. Instead, it automatically provisions storage by user request. Dynamic volume provisioning is based on an API object, StorageClass, referring to a Volume Plugin that provisions a Volume and the set of parameters to pass to the Volume Plugin.
- Ephemeral ContainerLINK[+]
If you want to investigate a Pod that's running with problems, you can add an ephemeral container to that Pod and carry out diagnostics. Ephemeral containers have no resource or scheduling guarantees, and you should not use them to run any part of the workload itself.
Each Event is a report of an event somewhere in the cluster. It generally denotes some state change in the system.[+]
Events have a limited retention time and triggers and messages may evolve with time. Event consumers should not rely on the timing of an event with a given reason reflecting a consistent underlying trigger, or the continued existence of events with that reason.
Events should be treated as informative, best-effort, supplemental data.
In Kubernetes, auditing generates a different kind of Event record (API group
Extensions are software components that extend and deeply integrate with Kubernetes to support new types of hardware.[+]
Many cluster administrators use a hosted or distribution instance of Kubernetes. These clusters come with extensions pre-installed. As a result, most Kubernetes users will not need to install extensions and even fewer users will need to author new ones.
Finalizers are namespaced keys that tell Kubernetes to wait until specific conditions are met before it fully deletes resources marked for deletion. Finalizers alert controllers to clean up resources the deleted object owned.[+]
When you tell Kubernetes to delete an object that has finalizers specified for it, the Kubernetes API marks the object for deletion by populating
.metadata.deletionTimestamp, and returns a
202status code (HTTP "Accepted"). The target object remains in a terminating state while the control plane, or other components, take the actions defined by the finalizers. After these actions are complete, the controller removes the relevant finalizers from the target object. When the
metadata.finalizersfield is empty, Kubernetes considers the deletion complete and deletes the object.
You can use finalizers to control garbage collection of resources. For example, you can define a finalizer to clean up related resources or infrastructure before the controller deletes the target resource.
FlexVolume is a deprecated interface for creating out-of-tree volume plugins. The Container Storage Interface is a newer interface that addresses several problems with FlexVolume.[+]
FlexVolumes enable users to write their own drivers and add support for their volumes in Kubernetes. FlexVolume driver binaries and dependencies must be installed on host machines. This requires root access. The Storage SIG suggests implementing a CSI driver if possible since it addresses the limitations with FlexVolumes.
- Garbage CollectionLINK
Garbage collection is a collective term for the various mechanisms Kubernetes uses to clean up cluster resources.[+]
- Helm ChartLINK
A package of pre-configured Kubernetes resources that can be managed with the Helm tool.[+]
Charts provide a reproducible way of creating and sharing Kubernetes applications. A single chart can be used to deploy something simple, like a memcached Pod, or something complex, like a full web app stack with HTTP servers, databases, caches, and so on.
- Horizontal Pod AutoscalerLINKまたの名を:HPA
An API resource that automatically scales the number of Pod replicas based on targeted CPU utilization or custom metric targets.[+]
- Init ContainerLINK
One or more initialization containers that must run to completion before any app containers run.[+]
Initialization (init) containers are like regular app containers, with one difference: init containers must run to completion before any app containers can start. Init containers run in series: each init container must run to completion before the next init container begins.
An open platform (not Kubernetes-specific) that provides a uniform way to integrate microservices, manage traffic flow, enforce policies, and aggregate telemetry data.[+]
Adding Istio does not require changing application code. It is a layer of infrastructure between a service and the network, which when combined with service deployments, is commonly referred to as a service mesh. Istio's control plane abstracts away the underlying cluster management platform, which may be Kubernetes, Mesosphere, etc.
A CLI tool that helps you create, destroy, upgrade and maintain production-grade, highly available, Kubernetes clusters.[+]Note: kops has general availability support only for AWS. Support for using kops with GCE and VMware vSphere are in alpha.
kopsprovisions your cluster with:
- Fully automated installation
- DNS-based cluster identification
- Self-healing: everything runs in Auto-Scaling Groups
- Limited OS support (Debian preferred, Ubuntu 16.04 supported, early support for CentOS & RHEL)
- High availability (HA) support
- The ability to directly provision, or to generate Terraform manifests
You can also build your own cluster using Kubeadm as a building block.
kopsbuilds on the kubeadm work.
- Kubernetes APILINK
The application that serves Kubernetes functionality through a RESTful interface and stores the state of the cluster.[+]
Kubernetes resources and "records of intent" are all stored as API objects, and modified via RESTful calls to the API. The API allows configuration to be managed in a declarative way. Users can interact with the Kubernetes API directly, or via tools like
kubectl. The core Kubernetes API is flexible and can also be extended to support custom resources.
- Managed ServiceLINK
A software offering maintained by a third-party provider.[+]
- Network PolicyLINK
A specification of how groups of Pods are allowed to communicate with each other and with other network endpoints.[+]
Network Policies help you declaratively configure which Pods are allowed to connect to each other, which namespaces are allowed to communicate, and more specifically which port numbers to enforce each policy on.
NetworkPolicyresources use labels to select Pods and define rules which specify what traffic is allowed to the selected Pods. Network Policies are implemented by a supported network plugin provided by a network provider. Be aware that creating a network resource without a controller to implement it will have no effect.
- Node-pressure evictionLINKまたの名を:kubelet eviction
Node-pressure eviction is the process by which the kubelet proactively terminates pods to reclaim resources on nodes.[+]
The kubelet monitors resources like CPU, memory, disk space, and filesystem inodes on your cluster's nodes. When one or more of these resources reach specific consumption levels, the kubelet can proactively fail one or more pods on the node to reclaim resources and prevent starvation.
Node-pressure eviction is not the same as API-initiated eviction.
An entity in the Kubernetes system. The Kubernetes API uses these entities to represent the state of your cluster.[+]
A Kubernetes object is typically a “record of intent”—once you create the object, the Kubernetes control plane works constantly to ensure that the item it represents actually exists. By creating an object, you're effectively telling the Kubernetes system what you want that part of your cluster's workload to look like; this is your cluster's desired state.
- Operator patternLINK[+]
You can extend Kubernetes by adding controllers to your cluster, beyond the built-in controllers that come as part of Kubernetes itself.
If a running application acts as a controller and has API access to carry out tasks against a custom resource that's defined in the control plane, that's an example of the Operator pattern.
- Pod DisruptionLINK
Pod disruption is the process by which Pods on Nodes are terminated either voluntarily or involuntarily.[+]
Voluntary disruptions are started intentionally by application owners or cluster administrators. Involuntary disruptions are unintentional and can be triggered by unavoidable issues like Nodes running out of resources, or by accidental deletions.
- Pod Disruption BudgetLINKまたの名を:PDB
A Pod Disruption Budget allows an application owner to create an object for a replicated application, that ensures a certain number or percentage of Pods with an assigned label will not be voluntarily evicted at any point in time.[+]
Involuntary disruptions cannot be prevented by PDBs; however they do count against the budget.
- Pod LifecycleLINK
The sequence of states through which a Pod passes during its lifetime.[+]
- Pod Security PolicyLINK
Enables fine-grained authorization of Pod creation and updates.[+]
A cluster-level resource that controls security sensitive aspects of the Pod specification. The
PodSecurityPolicyobjects define a set of conditions that a Pod must run with in order to be accepted into the system, as well as defaults for the related fields. Pod Security Policy control is implemented as an optional admission controller.
PodSecurityPolicy is deprecated as of Kubernetes v1.21, and will be removed in v1.25. We recommend migrating to Pod Security Admission, or a 3rd party admission plugin.
In computing, a proxy is a server that acts as an intermediary for a remote service.[+]
A client interacts with the proxy; the proxy copies the client's data to the actual server; the actual server replies to the proxy; the proxy sends the actual server's reply to the client.
You can run kube-proxy as a plain userland proxy service. If your operating system supports it, you can instead run kube-proxy in a hybrid mode that achieves the same overall effect using less system resources.
- QoS ClassLINK
QoS Class (Quality of Service Class) provides a way for Kubernetes to classify Pods within the cluster into several classes and make decisions about scheduling and eviction.[+]
QoS Class of a Pod is set at creation time based on its compute resources requests and limits settings. QoS classes are used to make decisions about Pods scheduling and eviction. Kubernetes can assign one of the following QoS classes to a Pod:
A whole-number representation of small or large numbers using SI suffixes.[+]
Quantities are representations of small or large numbers using a compact, whole-number notation with SI suffixes. Fractional numbers are represented using milli units, while large numbers can be represented using kilo, mega, or giga units.
For instance, the number
1.5is represented as
1500m, while the number
1000can be represented as
1M. You can also specify binary-notation suffixes; the number 2048 can be written as
The accepted decimal (power-of-10) units are
k(kilo, intentionally lowercase),
The accepted binary (power-of-2) units are
A workload resource that manages a replicated application, ensuring that a specific number of instances of a Pod are running.[+]
The control plane ensures that the defined number of Pods are running, even if some Pods fail, if you delete Pods manually, or if too many are started by mistake.Note: ReplicationController is deprecated. See Deployment, which is similar.
- Security ContextLINK[+]
securityContext, you can define: the user that processes run as, the group that processes run as, and privilege settings. You can also configure security policies (for example: SELinux, AppArmor or seccomp).
PodSpec.securityContextsetting applies to all containers in a Pod.
- Service BrokerLINK
An endpoint for a set of Managed Services offered and maintained by a third-party.[+]
Provides an identity for processes that run in a Pod.[+]
When processes inside Pods access the cluster, they are authenticated by the API server as a particular service account, for example,
default. When you create a Pod, if you do not specify a service account, it is automatically assigned the default service account in the same Namespace.
A technique for assigning requests to queues that provides better isolation than hashing modulo the number of queues.[+]
We are often concerned with insulating different flows of requests from each other, so that a high-intensity flow does not crowd out low-intensity flows. A simple way to put requests into queues is to hash some characteristics of the request, modulo the number of queues, to get the index of the queue to use. The hash function uses as input characteristics of the request that align with flows. For example, in the Internet this is often the 5-tuple of source and destination address, protocol, and source and destination port.
That simple hash-based scheme has the property that any high-intensity flow will crowd out all the low-intensity flows that hash to the same queue. Providing good insulation for a large number of flows requires a large number of queues, which is problematic. Shuffle-sharding is a more nimble technique that can do a better job of insulating the low-intensity flows from the high-intensity flows. The terminology of shuffle-sharding uses the metaphor of dealing a hand from a deck of cards; each queue is a metaphorical card. The shuffle-sharding technique starts with hashing the flow-identifying characteristics of the request, to produce a hash value with dozens or more of bits. Then the hash value is used as a source of entropy to shuffle the deck and deal a hand of cards (queues). All the dealt queues are examined, and the request is put into one of the examined queues with the shortest length. With a modest hand size, it does not cost much to examine all the dealt cards and a given low-intensity flow has a good chance to dodge the effects of a given high-intensity flow. With a large hand size it is expensive to examine the dealt queues and more difficult for the low-intensity flows to dodge the collective effects of a set of high-intensity flows. Thus, the hand size should be chosen judiciously.
- SIG (special interest group)LINK
sysctlis a semi-standardized interface for reading or changing the attributes of the running Unix kernel.
On Unix-like systems,
sysctlis both the name of the tool that administrators use to view and modify these settings, and also the system call that the tool uses.
Container runtimes and network plugins may rely on
sysctlvalues being set a certain way.
Taints and tolerations work together to ensure that pods are not scheduled onto inappropriate nodes. One or more taints are applied to a node. A node should only schedule a Pod with the matching tolerations for the configured taints.
A core object consisting of three required properties: key, value, and effect. Tolerations enable the scheduling of pods on nodes or node groups that have matching taints.[+]
- Upstream (disambiguation)LINK
May refer to: core Kubernetes or the source repo from which a repo was forked.[+]
- In the Kubernetes Community: Conversations often use upstream to mean the core Kubernetes codebase, which the general ecosystem, other code, or third-party tools rely upon. For example, community members may suggest that a feature is moved upstream so that it is in the core codebase instead of in a plugin or third-party tool.
- In GitHub or git: The convention is to refer to a source repo as upstream, whereas the forked repo is considered downstream.
- user namespaceLINK
A kernel feature to emulate root. Used for "rootless containers".[+]
User namespaces are a Linux kernel feature that allows a non-root user to emulate superuser ("root") privileges, for example in order to run containers without being a superuser outside the container.
User namespace is effective for mitigating damage of potential container break-out attacks.
In the context of user namespaces, the namespace is a Linux kernel feature, and not a namespace in the Kubernetes sense of the term.
- Volume PluginLINK
A Volume Plugin enables integration of storage within a Pod.[+]
A Volume Plugin lets you attach and mount storage volumes for use by a Pod. Volume plugins can be in tree or out of tree. In tree plugins are part of the Kubernetes code repository and follow its release cycle. Out of tree plugins are developed independently.
- WG (working group)LINK
Facilitates the discussion and/or implementation of a short-lived, narrow, or decoupled project for a committee, SIG, or cross-SIG effort.[+]