和kubernetes打交道少不了要写YAML，如果你和我一样需要经常手写YAML文件话，对apiVersion对象的定义有没有纠结过，它的Group、Version以及Kind该如何确定？或者根本就没想过，直接复制粘贴。直到我看完
Kubernetes API 资源使用：应该使用哪个 Group 和 Version?
这篇文章后才发现kubernetes从1.11.0版本开始已为我们准备了相关命令去获取我们当前集群所支持API的相关信息，这也是最准确的。随着kubernetes版本的迭代相关API也会做一定的调整，为什么别人的YAML文件在我这里kubectl apply的时候就报错啊，可能就是这个原因。详细关于kubernetes api的生命周期可以看一下这一篇。
Kubernetes使用声明式的 API 让系统更加健壮。但是这样也意味着我们需要通过使用CLI或者REST API来创建一个资源对象来告诉系统我们想要的操作。为此，我们需要定义 API 资源的名称、组和版本等信息。因为有太多的资源、太多的版本、太多的组了，而且都非常容易产生混淆，因此这会让用户感到很困惑。一个创建 Deployment 的YAML文件 ，里边会看到apiVersion: apps/v1beta2、apiVersion: apps/v1等等这样的信息，到底我们应该用哪一个呢？哪一个才是正确的呢？怎样确定Kubernetes集群支持的版本信息呢？其实这些信息简单的使用kubectl命令就可以获取到。
API Resources
我们可以通过下面的命令来获取Kubernetes集群支持的所有 API 资源：
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$ 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 proxy 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 proxy 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 proxy 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 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]
...
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注意：kubernetes集群1.11.0版本以上才支持api-resources命令
上面命令输出了很多有用的信息：
SHORTNAMES - 资源名称的简写，比如 deployments 简写就是 deploy，配合kubectl 快捷使用APIGROUP - API组，如果为空话代表core组，也就是核心API，查看官方文档可以了解更多详细信息KIND - 资源名称VERBS - 可用的方法，在你想要定义ClusterRole RBAC规则时很有用。你还可以选择获取特定 API 组的 API 资源，例如：
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$ 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]
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对于上面的每种资源类型，我们都可以使用kubectl explain命令来获取相关的资源详细信息：
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$ kubectl explain configmap
KIND: ConfigMap
VERSION: v1
DESCRIPTION:
ConfigMap holds configuration data for pods to consume.
FIELDS:
apiVersion <string>
APIVersion defines the versioned schema of this representation of an
object. Servers should convert recognized schemas to the latest internal
value, and may reject unrecognized values. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#resources
data <map[string]string>
Data contains the configuration data. Each key must consist of alphanumeric
characters, '-', '_' or '.'.
kind <string>
Kind is a string value representing the REST resource this object
represents. Servers may infer this from the endpoint the client submits
requests to. Cannot be updated. In CamelCase. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#types-kinds
metadata <Object>
Standard object's metadata. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata
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kubectl explain命令很有用，特别是在我们不知道该如何编写YAML文件的时候，可以使用该命令来帮助我们获得更多信息。
需要注意的是explain命令可能会显示旧版本的group/version，可以通过--api-version参数显示指定版本，比如：
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kubectl explain replicaset --api-version apps/v1
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API Versions
使用kubectl api-versions命令来获取集群支持的所有 API 版本：
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$ kubectl api-versions
admissionregistration.k8s.io/v1beta1
apiextensions.k8s.io/v1beta1
apiregistration.k8s.io/v1beta1
apps/v1
apps/v1beta1
apps/v1beta2
authentication.k8s.io/v1
authentication.k8s.io/v1beta1
authorization.k8s.io/v1
authorization.k8s.io/v1beta1
autoscaling/v1
autoscaling/v2beta1
batch/v1
batch/v1beta1
certificates.k8s.io/v1beta1
certmanager.k8s.io/v1alpha1
enterprises.upmc.com/v1
events.k8s.io/v1beta1
extensions/v1beta1
metrics.k8s.io/v1beta1
monitoring.coreos.com/v1
networking.k8s.io/v1
policy/v1beta1
rbac.authorization.k8s.io/v1
rbac.authorization.k8s.io/v1beta1
storage.k8s.io/v1
storage.k8s.io/v1beta1
v1
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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。
有的时候，我们只想确认特定的group/version是否可以用于某些资源。因为大多数的资源都支持GET方法，所以我们可以提供 下API 的 version 和group 然后尝试获取下资源，即可验证，kubectl get ..，例如：
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$ kubectl get deployments.v1.apps -n kube-system
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
autoscaler-aws-cluster-autoscaler 1 1 1 1 55d
calico-kube-controllers 1 1 1 1 317d
calico-policy-controller 0 0 0 0 317d
dns-controller 1 1 1 1 317d
elasticsearch-operator 1 1 1 1 274d
hpa-hpa-operator 1 1 1 1 60d
hpa-metrics-server 1 1 1 1 60d
kube-dns 2 2 2 2 317d
kube-dns-autoscaler 1 1 1 1 317d
spot-rescheduler-k8s-spot-rescheduler 1 1 1 1 136d
tiller-deploy 1 1 1 1 315d
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如果指定的group/version资源不存在或者资源本身就不存在，我们将会收到错误信息。
总结
本文将帮助您了解YAML文件中的kind和apiVersion这两个内容，如果你想了解更多关于Kubernetes设计的信息，我建议你查看下这篇文章。
参考
https://akomljen.com/kubernetes-api-resources-which-group-and-version-to-use/
https://kubernetes.io/zh/docs/concepts/overview/kubernetes-api/