在使用Kubernetes的时候，因为有太多的资源、太多的版本、太多的组了，这些都非常容易产生混淆。如果我们通过 YAML 文件定义过 Deployment 这样的资源清单文件的话，那么你应该会看到apiVersion: apps/v1beta2、apiVersion: apps/v1等等这样的信息，那么我们到底应该使用哪一个呢？哪一个才是正确的呢？如何检查Kubernetes集群支持哪些？其实我们使用kubectl工具就可以来解决我们的这些疑惑。
当前我使用的Kubernetes的版本是1.18.8。
API Resources
通过以下的命令来获取Kubernetes集群支持的所有 API 资源：
$ kubectl api-resources -o wide
NAME SHORTNAMES APIGROUP NAMESPACED KIND VERBS
bindings true Binding [create]
componentstatuses cs false ComponentStatus [get list]
configmaps cm true ConfigMap [create delete deletecollection get list patch update watch]
endpoints ep true Endpoints [create delete deletecollection get list patch update watch]
events ev true Event [create delete deletecollection get list patch update watch]
limitranges limits true LimitRange [create delete deletecollection get list patch update watch]
namespaces ns false Namespace [create delete get list patch update watch]
nodes no false Node [create delete deletecollection get list patch update watch]
persistentvolumeclaims pvc true PersistentVolumeClaim [create delete deletecollection get list patch update watch]
persistentvolumes pv false PersistentVolume [create delete deletecollection get list patch update watch]
pods po true Pod [create delete deletecollection get list patch update watch]
podtemplates true PodTemplate [create delete deletecollection get list patch update watch]
replicationcontrollers rc true ReplicationController [create delete deletecollection get list patch update watch]
resourcequotas quota true ResourceQuota [create delete deletecollection get list patch update watch]
secrets true Secret [create delete deletecollection get list patch update watch]
serviceaccounts sa true ServiceAccount [create delete deletecollection get list patch update watch]
services svc true Service [create delete get list patch update watch]
mutatingwebhookconfigurations admissionregistration.k8s.io false MutatingWebhookConfiguration [create delete deletecollection get list patch update watch]
validatingwebhookconfigurations admissionregistration.k8s.io false ValidatingWebhookConfiguration [create delete deletecollection get list patch update watch]
customresourcedefinitions crd,crds apiextensions.k8s.io false CustomResourceDefinition [create delete deletecollection get list patch update watch]
apiservices apiregistration.k8s.io false APIService [create delete deletecollection get list patch update watch]
controllerrevisions apps true ControllerRevision [create delete deletecollection get list patch update watch]
daemonsets ds apps true DaemonSet [create delete deletecollection get list patch update watch]
deployments deploy apps true Deployment [create delete deletecollection get list patch update watch]
replicasets rs apps true ReplicaSet [create delete deletecollection get list patch update watch]
statefulsets sts apps true StatefulSet [create delete deletecollection get list patch update watch]
tokenreviews authentication.k8s.io false TokenReview [create]
localsubjectaccessreviews authorization.k8s.io true LocalSubjectAccessReview [create]
selfsubjectaccessreviews authorization.k8s.io false SelfSubjectAccessReview [create]
selfsubjectrulesreviews authorization.k8s.io false SelfSubjectRulesReview [create]
subjectaccessreviews authorization.k8s.io false SubjectAccessReview [create]
horizontalpodautoscalers hpa autoscaling true HorizontalPodAutoscaler [create delete deletecollection get list patch update watch]
cronjobs cj batch true CronJob [create delete deletecollection get list patch update watch]
jobs batch true Job [create delete deletecollection get list patch update watch]
certificatesigningrequests csr certificates.k8s.io false CertificateSigningRequest [create delete deletecollection get list patch update watch]
leases coordination.k8s.io true Lease [create delete deletecollection get list patch update watch]
endpointslices discovery.k8s.io true EndpointSlice [create delete deletecollection get list patch update watch]
events ev events.k8s.io true Event [create delete deletecollection get list patch update watch]
ingresses ing extensions true Ingress [create delete deletecollection get list patch update watch]
ingressclasses networking.k8s.io false IngressClass [create delete deletecollection get list patch update watch]
ingresses ing networking.k8s.io true Ingress [create delete deletecollection get list patch update watch]
networkpolicies netpol networking.k8s.io true NetworkPolicy [create delete deletecollection get list patch update watch]
runtimeclasses node.k8s.io false RuntimeClass [create delete deletecollection get list patch update watch]
poddisruptionbudgets pdb policy true PodDisruptionBudget [create delete deletecollection get list patch update watch]
podsecuritypolicies psp policy false PodSecurityPolicy [create delete deletecollection get list patch update watch]
clusterrolebindings rbac.authorization.k8s.io false ClusterRoleBinding [create delete deletecollection get list patch update watch]
clusterroles rbac.authorization.k8s.io false ClusterRole [create delete deletecollection get list patch update watch]
rolebindings rbac.authorization.k8s.io true RoleBinding [create delete deletecollection get list patch update watch]
roles rbac.authorization.k8s.io true Role [create delete deletecollection get list patch update watch]
priorityclasses pc scheduling.k8s.io false PriorityClass [create delete deletecollection get list patch update watch]
csidrivers storage.k8s.io false CSIDriver [create delete deletecollection get list patch update watch]
csinodes storage.k8s.io false CSINode [create delete deletecollection get list patch update watch]
storageclasses sc storage.k8s.io false StorageClass [create delete deletecollection get list patch update watch]
volumeattachments storage.k8s.io false VolumeAttachment [create delete deletecollection get list patch update watch]
以上可以看到：
SHORTNAMES- 资源名称的简写，比如 deployments 简写就是 deploy，我们可以将这些快捷方式与kubectl一起使用APIGROUP- 我们可以查看官方文档以了解更多信息，但简而言之，您将在yaml文件中使用它像apiVersion：<APIGROUP>/v1KIND- 资源名称VERBS- 可用的方法，在您想要定义ClusterRole RBAC规则时也很有用
您还可以选择获取特定 API 组的 API 资源，例如：
$ kubectl api-resources --api-group apps -o wide
NAME SHORTNAMES APIGROUP NAMESPACED KIND VERBS
controllerrevisions apps true ControllerRevision [create delete deletecollection get list patch update watch]
daemonsets ds apps true DaemonSet [create delete deletecollection get list patch update watch]
deployments deploy apps true Deployment [create delete deletecollection get list patch update watch]
replicasets rs apps true ReplicaSet [create delete deletecollection get list patch update watch]
statefulsets sts apps true StatefulSet [create delete deletecollection get list patch update watch]
Kubectl Explain
可以使用kubectl explain命令来获取有关的资源详细信息：
$ kubectl explain deployment.spec
KIND: Deployment
VERSION: apps/v1
RESOURCE: spec <Object>
DESCRIPTION:
Specification of the desired behavior of the Deployment.
DeploymentSpec is the specification of the desired behavior of the
Deployment.
FIELDS:
minReadySeconds <integer>
Minimum number of seconds for which a newly created pod should be ready
without any of its container crashing, for it to be considered available.
Defaults to 0 (pod will be considered available as soon as it is ready)
paused <boolean>
Indicates that the deployment is paused.
progressDeadlineSeconds <integer>
The maximum time in seconds for a deployment to make progress before it is
considered to be failed. The deployment controller will continue to process
failed deployments and a condition with a ProgressDeadlineExceeded reason
will be surfaced in the deployment status. Note that progress will not be
estimated during the time a deployment is paused. Defaults to 600s.
replicas <integer>
Number of desired pods. This is a pointer to distinguish between explicit
zero and not specified. Defaults to 1.
revisionHistoryLimit <integer>
The number of old ReplicaSets to retain to allow rollback. This is a
pointer to distinguish between explicit zero and not specified. Defaults to
10.
selector <Object> -required-
Label selector for pods. Existing ReplicaSets whose pods are selected by
this will be the ones affected by this deployment. It must match the pod
template's labels.
strategy <Object>
The deployment strategy to use to replace existing pods with new ones.
template <Object> -required-
Template describes the pods that will be created.
kubectl explain命令非常有用，特别是在我们不知道该如何编写YAML文件的时候，就可以使用改命令来帮助我们获得更多提示信息。
需要注意的是explain命令可能会显示旧的group/version，我们可以通过--api-version参数显示设置它，比如： 请注意，explain可能会显示旧组/版本，但您可以使用–api-version显式设置它，例如：
$ kubectl explain deployment.spec --api-version apps/v1
API Versions
使用下面的命令来获取集群支持的所有 API 版本：
$ kubectl api-versions
admissionregistration.k8s.io/v1
admissionregistration.k8s.io/v1beta1
apiextensions.k8s.io/v1
apiextensions.k8s.io/v1beta1
apiregistration.k8s.io/v1
apiregistration.k8s.io/v1beta1
apps/v1
authentication.k8s.io/v1
authentication.k8s.io/v1beta1
authorization.k8s.io/v1
authorization.k8s.io/v1beta1
autoscaling/v1
autoscaling/v2beta1
autoscaling/v2beta2
batch/v1
batch/v1beta1
certificates.k8s.io/v1beta1
coordination.k8s.io/v1
coordination.k8s.io/v1beta1
discovery.k8s.io/v1beta1
events.k8s.io/v1beta1
extensions/v1beta1
networking.k8s.io/v1
networking.k8s.io/v1beta1
node.k8s.io/v1beta1
policy/v1beta1
rbac.authorization.k8s.io/v1
rbac.authorization.k8s.io/v1beta1
scheduling.k8s.io/v1
scheduling.k8s.io/v1beta1
storage.k8s.io/v1
storage.k8s.io/v1beta1
v1
输出结果是以group/version的方式呈现的，可以通过查看此页面了解更多有关Kubernetes中 API 版本控制的信息。
可以通过kubectl get <API_RESOURCE_NAME>.<API_VERSION>.<API_GROUP>来查看特定的group/version是否可以用于某些资源：
$ kubectl get deployments.v1.apps -n kube-system
NAME READY UP-TO-DATE AVAILABLE AGE
coredns 2/2 2 2 52m
如果资源不存在指定的group/version组合或者资源根本不存在，我们将会收到错误信息：
$ kubectl get deployments.v1beta.apps -n kube-system
error: the server doesn't have a resource type "deployments"
总结
本文将帮助您了解 Kubernetes YAML 文件中的kind和apiVersion这两个内容，在不同Kubernetes版本这两个字段会有所变更。
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