6、Kubernetes Pod控制器应用进阶

定义pod时，在spec字段中常用的定义字段有哪些？

master ~]# kubectl explain pods.spec.containers

KIND:     Pod
VERSION:  v1

RESOURCE: containers <[]Object>

DESCRIPTION:
     List of containers belonging to the pod. Containers cannot currently be
     added or removed. There must be at least one container in a Pod. Cannot be
     updated.

     A single application container that you want to run within a pod.

FIELDS:
   args    <[]string>
     Arguments to the entrypoint. The docker image's CMD is used if this is not
     provided. Variable references $(VAR_NAME) are expanded using the
     container's environment. If a variable cannot be resolved, the reference in
     the input string will be unchanged. The $(VAR_NAME) syntax can be escaped
     with a double $$, ie: $$(VAR_NAME). Escaped references will never be
     expanded, regardless of whether the variable exists or not. Cannot be
     updated. More info:
     https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#running-a-command-in-a-shell

   command    <[]string>
     Entrypoint array. Not executed within a shell. The docker image's
     ENTRYPOINT is used if this is not provided. Variable references $(VAR_NAME)
     are expanded using the container's environment. If a variable cannot be
     resolved, the reference in the input string will be unchanged. The
     $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME).
     Escaped references will never be expanded, regardless of whether the
     variable exists or not. Cannot be updated. More info:
     https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#running-a-command-in-a-shell

   env    <[]Object>
     List of environment variables to set in the container. Cannot be updated.

   envFrom    <[]Object>
     List of sources to populate environment variables in the container. The
     keys defined within a source must be a C_IDENTIFIER. All invalid keys will
     be reported as an event when the container is starting. When a key exists
     in multiple sources, the value associated with the last source will take
     precedence. Values defined by an Env with a duplicate key will take
     precedence. Cannot be updated.

   image    <string>
     Docker image name. More info:
     https://kubernetes.io/docs/concepts/containers/images This field is
     optional to allow higher level config management to default or override
     container images in workload controllers like Deployments and StatefulSets.

   imagePullPolicy    <string>
     Image pull policy. One of Always, Never, IfNotPresent. Defaults to Always
     if :latest tag is specified, or IfNotPresent otherwise. Cannot be updated.
     More info:
     https://kubernetes.io/docs/concepts/containers/images#updating-images

   lifecycle    <Object>
     Actions that the management system should take in response to container
     lifecycle events. Cannot be updated.

   livenessProbe    <Object>
     Periodic probe of container liveness. Container will be restarted if the
     probe fails. Cannot be updated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

   name    <string> -required-
     Name of the container specified as a DNS_LABEL. Each container in a pod
     must have a unique name (DNS_LABEL). Cannot be updated.

   ports    <[]Object>
     List of ports to expose from the container. Exposing a port here gives the
     system additional information about the network connections a container
     uses, but is primarily informational. Not specifying a port here DOES NOT
     prevent that port from being exposed. Any port which is listening on the
     default "0.0.0.0" address inside a container will be accessible from the
     network. Cannot be updated.

   readinessProbe    <Object>
     Periodic probe of container service readiness. Container will be removed
     from service endpoints if the probe fails. Cannot be updated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

   resources    <Object>
     Compute Resources required by this container. Cannot be updated. More info:
     https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/

   securityContext    <Object>
     Security options the pod should run with. More info:
     https://kubernetes.io/docs/concepts/policy/security-context/ More info:
     https://kubernetes.io/docs/tasks/configure-pod-container/security-context/

   stdin    <boolean>
     Whether this container should allocate a buffer for stdin in the container
     runtime. If this is not set, reads from stdin in the container will always
     result in EOF. Default is false.

   stdinOnce    <boolean>
     Whether the container runtime should close the stdin channel after it has
     been opened by a single attach. When stdin is true the stdin stream will
     remain open across multiple attach sessions. If stdinOnce is set to true,
     stdin is opened on container start, is empty until the first client
     attaches to stdin, and then remains open and accepts data until the client
     disconnects, at which time stdin is closed and remains closed until the
     container is restarted. If this flag is false, a container processes that
     reads from stdin will never receive an EOF. Default is false

   terminationMessagePath    <string>
     Optional: Path at which the file to which the container's termination
     message will be written is mounted into the container's filesystem. Message
     written is intended to be brief final status, such as an assertion failure
     message. Will be truncated by the node if greater than  bytes. The
     total message length across all containers will be limited to 12kb.
     Defaults to /dev/termination-log. Cannot be updated.

   terminationMessagePolicy    <string>
     Indicate how the termination message should be populated. File will use the
     contents of terminationMessagePath to populate the container status message
     on both success and failure. FallbackToLogsOnError will use the last chunk
     of container log output if the termination message file is empty and the
     container exited with an error. The log output is limited to  bytes or
      lines, whichever is smaller. Defaults to File. Cannot be updated.

   tty    <boolean>
     Whether this container should allocate a TTY for itself, also requires
     'stdin' to be true. Default is false.

   volumeDevices    <[]Object>
     volumeDevices is the list of block devices to be used by the container.
     This is a beta feature.

   volumeMounts    <[]Object>
     Pod volumes to mount into the container's filesystem. Cannot be updated.

   workingDir    <string>
     Container's working directory. If not specified, the container runtime's
     default will be used, which might be configured in the container image.
     Cannot be updated.

修改镜像中的默认应用：为容器设置启动时要执行的命令及其入参

https://kubernetes.io/zh/docs/tasks/inject-data-application/define-command-argument-container/

Docker 与 Kubernetes中对应的字段名称

标签

一个资源可以拥有多个标签，同一个标签可以被添加至多个资源对象；

标签可以在资源创建时指定，

标签：

key=value

key：字母、数字、_、-、.

value：可以为空，只能字母或数字开头及结尾，中间可使用字母、数字、_、-、.

查看标签

master manifests]# kubectl create -f pod-demo.yaml
pod/pod-demo created

master ~]# kubectl get pods --show-labels

NAME                           READY   STATUS             RESTARTS   AGE     LABELS
client                         /     Error                        12d     run=client
client1                        /     Completed                    11d     run=client1
client2                        /     Error                        2d7h    run=client2
client3                        /     Error                        2d6h    run=client3
myapp-5bc569c47d-5cdpw         /     Running                      2d3h    pod-template-hash=5bc569c47d,run=myapp
myapp-5bc569c47d-c4gr2         /     Running                      2d3h    pod-template-hash=5bc569c47d,run=myapp
myapp-5bc569c47d-njr5w         /     Running                      2d3h    pod-template-hash=5bc569c47d,run=myapp
nginx-deploy-55d8d67cf-hlj9v   /     Running                      12d     pod-template-hash=55d8d67cf,run=nginx-deploy
pod-demo                       /     ImagePullBackOff             8m23s   app=myapp,tier=frontend

# kubectl get pods -L app  //-L选项用于显示指定资源对象类别下的所有资源的对应的标签的值

# kubectl get pods -l app  //做标签过滤

NAME       READY   STATUS             RESTARTS   AGE
pod-demo   /     ImagePullBackOff             12m

# kubectl get pods -l app --show-labels

NAME       READY   STATUS             RESTARTS   AGE   LABELS
pod-demo   /     ImagePullBackOff             13m   app=myapp,tier=frontend

如何打标签

# kubectl label --help   //打标签的用法

Usage:
kubectl label [--overwrite] (-f FILENAME | TYPE NAME) KEY_1=VAL_1 ... KEY_N=VAL_N [--resource-version=version]

# kubectl label pods pod-demo release=canary  //打标签
pod/pod-demo labeled
# kubectl get pods -l app --show-labels
NAME       READY   STATUS    RESTARTS   AGE    LABELS
pod-demo   /     Running             165m   app=myapp,release=canary,tier=frontend

# kubectl label pods pod-demo release=stable  //强行打标会报错
error: 'release' already has a value (canary), and --overwrite is false

# kubectl label pods pod-demo release=stable --overwrite  //此处需要将替换的标签进行覆盖
pod/pod-demo labeled
# kubectl get pods -l app --show-labels
NAME       READY   STATUS    RESTARTS   AGE    LABELS
pod-demo   /     Running             167m   app=myapp,release=stable,tier=frontend

标签选择器：

等值关系：=，==，!=

集合关系：

KEY in(VALUE1,VALUE2,...)

KEY notin(VALUE1,VALUE2,...)

KEY  存在此键

!KEY 不存在此键

等值关系示例：
# kubectl get pods -l release=stable --show-labels
NAME       READY   STATUS    RESTARTS   AGE    LABELS
pod-demo   /     Running             172m   app=myapp,release=stable,tier=frontend

集合关系示例：
# kubectl get pods -l "release in (stable,beta,alpha)" --show-labels
NAME       READY   STATUS    RESTARTS   AGE    LABELS
pod-demo   /     Running             3h5m   app=myapp,release=stable,tier=frontend
# kubectl get pods -l "release notin (stable,beta,alpha)" --show-labels
NAME                           READY   STATUS      RESTARTS   AGE     LABELS
client                         /     Error                 12d     run=client
client1                        /     Completed             12d     run=client1
client2                        /     Error                 2d10h   run=client2
client3                        /     Error                 2d9h    run=client3
myapp-5bc569c47d-5cdpw         /     Running               2d6h    pod-template-hash=5bc569c47d,run=myapp
myapp-5bc569c47d-c4gr2         /     Running               2d6h    pod-template-hash=5bc569c47d,run=myapp
myapp-5bc569c47d-njr5w         /     Running               2d6h    pod-template-hash=5bc569c47d,run=myapp
nginx-deploy-55d8d67cf-hlj9v   /     Running               12d     pod-template-hash=55d8d67cf,run=nginx-deploy

许多资源支持内嵌字段定义其使用标签选择器

matchLabels：直接给定键值

matchExpressions：基于给定的表达式来定义使用的标签选择器，{key:"KEY",operator:"OPERATOR",values:[VAL1,VAL2,...]}，表示意思是：将KEY和VAL1、VAL2通过操作符OPERATOR进行比较;

操作符：

In，Notin：其values字段必须为非空列表；

Exists，NotExists：其values字段必须为空列表。

不但可以为pod打标签，各种对象都可以打标签

# kubectl get nodes --show-labels
NAME     STATUS   ROLES    AGE   VERSION   LABELS
master   Ready    master   15d   v1.14.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=master,kubernetes.io/os=linux,node-role.kubernetes.io/master=
node01   Ready    <none>   13d   v1.14.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=node01,kubernetes.io/os=linux
node02   Ready    <none>   15d   v1.14.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=node02,kubernetes.io/os=linux
node03   Ready    <none>   13d   v1.14.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=node03,kubernetes.io/os=linux

# kubectl label nodes node01 disktype=ssd  //为node01节点打标签
node/node01 labeled

# kubectl get nodes --show-labels
NAME     STATUS   ROLES    AGE   VERSION   LABELS
master   Ready    master   15d   v1.14.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=master,kubernetes.io/os=linux,node-role.kubernetes.io/master=
node01   Ready    <none>   13d   v1.14.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,disktype=ssd,kubernetes.io/arch=amd64,kubernetes.io/hostname=node01,kubernetes.io/os=linux
node02   Ready    <none>   15d   v1.14.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=node02,kubernetes.io/os=linux
node03   Ready    <none>   13d   v1.14.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=node03,kubernetes.io/os=linux

节点带有标签的好处在于在添加资源时，可以让资源对带有某标签的节点具有倾向性

# kubectl explain pods.spec

 nodeSelector    <map[string]string>映射值  //节点选择器，可以限定pod运行在哪个节点上
     NodeSelector is a selector which must be true for the pod to fit on a node.
     Selector which must match a node's labels for the pod to be scheduled on
     that node. More info:
     https://kubernetes.io/docs/concepts/configuration/assign-pod-node/

   nodeName    <string>  //节点名称
     NodeName is a request to schedule this pod onto a specific node. If it is
     non-empty, the scheduler simply schedules this pod onto that node, assuming
     that it fits resource requirements.

示例：

pod-demo运行在node02上，如果想让pod-demo运行在node01上，可以在yaml文件中添加标签选择器

# kubectl get pods -o wide
NAME                           READY   STATUS      RESTARTS   AGE     IP            NODE     NOMINATED NODE   READINESS GATES
...........
pod-demo                       2/2     Running     3          3h57m   10.244.2.10   node02   <none>           <none>

master manifests]# vim pod-demo.yaml

   apiVersion: v1
   kind: Pod
   metadata:
     name: pod-demo
     namespace: default
     labels:
       app: myapp
       tier: frontend
   spec:
 10   containers:
    - name: myapp
      image: ikubernetes/myapp:v1
    - name: busybox
      image: busybox:latest
      command:
      - "/bin/sh"
      - "-c"
      - "sleep 3600"
 19   nodeSelector:   //此处要和上面的container对齐，因为这里不是容器的属性，而是pod的属性
      disktype: ssd

# kubectl create -f pod-demo.yaml   //重新创建pod

# kubectl describe pods pod-demo

Name:               pod-demo
Namespace:          default
Priority:
PriorityClassName:  <none>
Node:               node01/192.168.184.142
........
Events:
  Type     Reason     Age                From               Message
  ----     ------     ----               ----               -------
  Normal   Scheduled  2m1s               default-scheduler  Successfully assigned default/pod-demo to node01

annotations：资源也可以使用注解，也是键值类型的

与label不同的地方在于，annotations不能用于挑选资源对象，仅用于为对象提供"元数据"

查看资源注解：

# kubectl describe pod-demo

# kubectl describe pods pod-demo
Name:         pod-demo
Namespace:    default
Priority:
Node:         knode3/10.129.7.224
Start Time:   Wed,  May  :: +
Labels:       app=myapp
              tier=frontend
Annotations:  <none>    //此时是空的
Status:       Running

# kubectl delete -f pod-damo.yaml    //先删除pod，然后再yaml文件中添加

apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  namespace: default
  labels:
    app: myapp
    tier: frontend
  annotations:    //此处添加资源注解
    zhou/created-by: "cluster admin"  //zhou表示组织即由哪个组织添加，created-by是键，cluster admin是值；
spec:

# kubectl create -f pod-damo.yaml

# kubectl describe pods pod-demo

Annotations:  zhou/created-by: cluster admin  //会有此行注解

pod的生命周期：官方参考

Pod状态与生命周期管理

pod状态的unknown状态
pod所处的状态信息，是api server跟运行这个pod的节点上kubelet通信，进而获取的pod状态信息。
如果pod所处的node上的kubelet故障，那么api server就无法获取pod的信息，此时pod的节点就是unknown；

创建pod过程详解：
当用户创建pod时，这个请求就会提交给api server，api server会先把创建请求的目标状态保存到etcd中，api server接下来会请求scheduler进行调度(scheduler需要负责挑选一个合理的节点运行pod)；如果调度成功，会把调度结果存到etcd中；一旦存到etcd中并完成更新，那么这个请求所调度到的节点，比如这个请求被调度到node2节点，那么node2上的kubelet通过api server中的状态变化得知有一个新任务，此时kubelet会拿到此前用户提交的pod创建清单，kubelet会根据清单在node2上创建并启动pod，无论创建成功或者失败，pod都会有一个当前结果status，这个当前结果状态就会被发送给api server，然后由api server存到etcd中。

pod生命周期的重要行为：

初始化容器：
容器探测：

liveness
readiness

restartpolicy：pod的重启策略

Always，Onfailure，Never，Default to Always

探针类型三种：

ExecAction、TcpSocketAction、HTTPAction

# kubectl explain pods.spec.containers

lifecycle    <Object>
     Actions that the management system should take in response to container
     lifecycle events. Cannot be updated.

   livenessProbe    <Object>
     Periodic probe of container liveness. Container will be restarted if the
     probe fails. Cannot be updated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

readinessProbe    <Object>
     Periodic probe of container service readiness. Container will be removed
     from service endpoints if the probe fails. Cannot be updated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

# kubectl explain pods.spec.containers.livenessProbe

KIND:     Pod
VERSION:  v1

RESOURCE: livenessProbe <Object>

DESCRIPTION:
     Periodic probe of container liveness. Container will be restarted if the
     probe fails. Cannot be updated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

     Probe describes a health check to be performed against a container to
     determine whether it is alive or ready to receive traffic.

FIELDS:
   exec    <Object>
     One and only one of the following should be specified. Exec specifies the
     action to take.

   failureThreshold    <integer>
     Minimum consecutive failures for the probe to be considered failed after
     having succeeded. Defaults to . Minimum value is .

   httpGet    <Object>
     HTTPGet specifies the http request to perform.

   initialDelaySeconds    <integer>
     Number of seconds after the container has started before liveness probes
     are initiated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

   periodSeconds    <integer>
     How often (in seconds) to perform the probe. Default to  seconds. Minimum
     value is .

   successThreshold    <integer>
     Minimum consecutive successes for the probe to be considered successful
     after having failed. Defaults to . Must be  for liveness and startup.
     Minimum value is .

   tcpSocket    <Object>
     TCPSocket specifies an action involving a TCP port. TCP hooks not yet
     supported

# kubectl explain pods.spec.containers.livenessProbe.exec   //exec探测测试，直接执行自定义的命令进行探测

KIND:     Pod
VERSION:  v1

RESOURCE: exec <Object>

DESCRIPTION:
     One and only one of the following should be specified. Exec specifies the
     action to take.

     ExecAction describes a "run in container" action.

FIELDS:
   command    <[]string>
     Command is the command line to execute inside the container, the working
     directory for the command is root ('/') in the container's filesystem. The
     command is simply exec'd, it is not run inside a shell, so traditional
     shell instructions ('|', etc) won't work. To use a shell, you need to
     explicitly call out to that shell. Exit status of  is treated as
     live/healthy and non-zero is unhealthy.

# vim livenes.exec.yaml

apiVersion: v1
kind: Pod
metadata:
  name: livene-exec-pod
  namespace: default
spec:
  containers:
  - name: liveness-exec-container
    image: busybox:latest
    imagePullPolicy: IfNotPresent
    command: ["/bin/sh","-c","touch /tmp/healthy; sleep 30; rm -rf /tmp/healthy; sleep 3600"]
    livenessProbe:
      exec:
        command: ["test","-e","/tmp/healthy"]
      initialDelaySeconds:
      periodSeconds: 

# kubectl create -f livenes.exec.yaml
# kubectl explain pods.spec.containers.livenessProbe.tcpSocket
# kubectl explain pods.spec.containers.livenessProbe.httpGet

使用pod必须要做readinessProbe和livenessProbe的原因：

比如一个pod运行的是一个web站点，从pod启动到web站点就绪可能需要5秒钟甚至更多；
在这几秒钟的时间里，可能pod已经启动起来，但是web站点服务还没有准备好，这是web服务是不能被访问到的；
所以就绪性探测和service调度有着重要的关联性；
service为动态的、有生命周期的pod资源提供了一个固定访问入口端点，因此客户端访问时直接访问service；
service使用标签选择器关联至各pod资源，那么如果创建了一个pod资源，且这个pod资源正好符合标签选择器的选择条件，
那么service就会立即把这个新创建的pod作为后端调度的对象，当用户请求进service时，那么新的请求就有可能被调度至刚才新创建的pod，
但是这个新pod是在刚刚被创建成功时关联进service的，但是pod的web服务很可能还没有就绪，因此请求得到的结果就是失败的；
但是我们期望的是service把请求调度到每一个关联的pod上来时，pod内的服务一定时就绪的，因此如果pod在创建时没有就绪性探测，
那么可能来自service的请求就会失败，所以在pod创建中，readinessProbe是很有必要的；
livenessprobe是探测pod存活，readinessprobe是探测就绪；
示例：
# vim readiness-httpget.yaml

apiVersion: v1
kind: Pod
metadata:
  name: readiness-httpget-pod
  namespace: default
spec:
  containers:
  - name: readiness-httpget-container
    image: ikubernetes/myapp:v1
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort:
    readinessProbe:
      httpGet:
        port: http
        path: /index.html
      initialDelaySeconds:
      periodSeconds: 

# kubectl create -f readiness-httpget.yaml
# kubectl get pods   //此时查看，readiness-httpget-pod是就绪的，但是如果网页文件不存在，那么就不会就绪了
# kubectl exec -it readiness-httpget-pod -- /bin/sh
# rm -f /usr/share/nginx/html/index.html   //此时就绪的pod就是0个，此时pod运行，但是网页文件不存在

# kubectl explain pods.spec.containers.lifecycle  //生命周期的启动后钩子和终止前钩子

KIND:     Pod
VERSION:  v1

RESOURCE: lifecycle <Object>

DESCRIPTION:
     Actions that the management system should take in response to container
     lifecycle events. Cannot be updated.

     Lifecycle describes actions that the management system should take in
     response to container lifecycle events. For the PostStart and PreStop
     lifecycle handlers, management of the container blocks until the action is
     complete, unless the container process fails, in which case the handler is
     aborted.

FIELDS:
   postStart    <Object>   //启动后
     PostStart is called immediately after a container is created. If the
     handler fails, the container is terminated and restarted according to its
     restart policy. Other management of the container blocks until the hook
     completes. More info:
     https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks

   preStop    <Object>   //终止前
     PreStop is called immediately before a container is terminated due to an
     API request or management event such as liveness/startup probe failure,
     preemption, resource contention, etc. The handler is not called if the
     container crashes or exits. The reason for termination is passed to the
     handler. The Pod's termination grace period countdown begins before the
     PreStop hooked is executed. Regardless of the outcome of the handler, the
     container will eventually terminate within the Pod's termination grace
     period. Other management of the container blocks until the hook completes
     or until the termination grace period is reached. More info:
     https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks

# kubectl explain pods.spec.containers.lifecycle.postStart

# kubectl explain pods.spec.containers.lifecycle.preStop

定义postStop，即在pod启动后立即执行一个钩子

比如镜像中自带了一个httpd运行web服务，但是没有默认的目录和页面存在，因此做一个在pod启动后立即执行钩子；

比如创建一个目录并创建一个网页，然后在启动http，看两个是否能够关联起来

# cat poststart.yaml

apiVerion: v1
kind: Pod
metadata:
    name: poststart-pod
    namepace: default
spec:
    containers:
    - name: busy-httpd
      image: busybox: latest
      imagePullPolicy: IfNotPresent
      lifecycle:
        postStart:
          exec:
            command: [/bin/sh","-c","mkdir -p/data/web/html"]   /此command是定义pod启动后执行的初始化任务
      command: ["/bin/sh","-c","sleep 3600"]    //此command是定义容器中的command，当容器启动后，先执行此command，然后执行args命令，然后执行lifecycle的postStart，然而/bin/httpd依赖于上面command的执行结果
      #args: ["-f","mkdir -p /data/web/html","-h /data/web/html"]  //使用args传递参数，-f是运行在前台，-h是指定表示家目录

kubectl create -f poststart.yaml