apiversion：group/apiversion	#如果没有给定group名称，那么默认为core，可以使用kubect1 api-versions#获取当前k8s版本上所有的apiVersion版本信息（每个版本可能不同）
kind:	#资源类别
metadata:	#资源元数据
    name
	namespace
	lables
	annotations	#主要目的是方便用户阅读查找
spec:	#期望的状态（disired state）
status:	#当前状态，本字段有Kubernetes自身维护，用户不能去定义

kubectl api-versions 

kubectl explain pod
KIND:     Pod
VERSION:  v1

kubectl  explain pod.apiVersion
KIND:     Pod
VERSION:  v1

kubectl explain ingress
KIND:     Ingress
VERSION:  networking.k8s.io/v1

apiVersion	<string>	#表示字符串类型
kind	<string>
metadata	<Object>	#表示需要嵌套多层字段
labels <map[string]string>	#表示由k:v组成的映射
finalizers	<[]string>	#表示字串列表
ownerReferences	<[]Object>	#表示对象列表
hostPID	<boolean>	#布尔类型
priority	<integer>	#整形
name	<string>	-required-	#如果类型后面接-required-,表示为必值字段
spec	<Object>		#
status	<Object>

编写POD文件一个POD运行两个容器
vim pods-demo.yaml
apiVersion: v1
kind: Pod
metadata:
  name: app-pod
  labels:
    app: app
    version: v1
spec:
  containers:
  - name: appname
    image: nginx
  - name: apptest
    image: nginx
	
创建POD
kubectl apply -f pods-demo.yaml
会发现容器名称为apptest启动失败

排错思路
查看POD状态
kubectl get pods
查看容器中的信息，查看状态和事件
kubectl describe pod
查看容器中的日志信息，多个容器需要加-c，指定容器名称
kubectl log app-pod -c apptest	#可以看到是端口冲突
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: ipv6 not available
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2021/03/19 05:11:17 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
2021/03/19 05:11:17 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
2021/03/19 05:11:17 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
2021/03/19 05:11:17 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
2021/03/19 05:11:17 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
2021/03/19 05:11:17 [emerg] 1#1: still could not bind()
nginx: [emerg] still could not bind()

查看pods详细信息，看POD运行在哪个节点上
kubectl get pods -o wide
实时刷新POD状态
kubectl get pods -w

解决方法
删除第二个容器，或者修改容器端口，一个POD中端口不可以冲突

[root@k8s-master test]# cat init-damo.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod 
  labels: 
    app: myapp 
spec:
  containers:
  - name: myapp-container 
    image: busybox
    command: [‘sh‘, ‘-c‘, ‘echo The app is running! && sleep 3600‘] 
  initContainers: 
  - name: init-myservice
    image: busybox
    command: [‘sh‘, ‘-c‘, ‘until nslookup myservice; do echo waiting for myservice; sleep 2; done;‘] 
  - name: init-mydb 
    image: busybox 
    command: [‘sh‘, ‘-c‘, ‘until nslookup mydb; do echo waiting for mydb; sleep 2; done;‘]

创建POD
kubectl apply -f init-damo.yaml

发现POD状态一直不成功，INITC两个没有处理完
[root@k8s-master test]# kubectl get pods
NAME        READY   STATUS     RESTARTS   AGE
myapp-pod   0/1     Init:0/2   0          2m57s

[root@k8s-master test]# kubectl describe pods myapp-pod
Init Containers:
  init-myservice:
    Ready:          False	#查看此INIT状态是失败的
	
创建一个myservice文件，第一个INITC，模拟后端服务的条件
[root@k8s-master test]# cat myservice.yaml 
kind: Service 
apiVersion: v1 
metadata: 
  name: myservice 
spec: 
  ports: 
  - protocol: TCP 
    port: 80 
    targetPort: 9376

创建svc
kubectl apply -f myservice.yaml
[root@k8s-master test]# kubectl get pods 
NAME        READY   STATUS     RESTARTS   AGE
myapp-pod   0/1     Init:1/2   0          17m

[root@k8s-master test]# kubectl describe pods myapp-po
Init Containers:
  init-myservice:
    Ready:          True	#启动成功
	
创建一个myservice文件，第一个INITC，模拟后端服务的条件
[root@k8s-master test]# cat mydb.yaml 
kind: Service 
apiVersion: v1 
metadata: 
  name: mydb 
spec: 
  ports: 
  - protocol: TCP 
    port: 80 
    targetPort: 9377 

创建第二个SVC
kubectl apply -f mydb.yaml

查看POD日志
[root@k8s-master test]# kubectl logs myapp-pod
The app is running!

查看pod状态
[root@k8s-master test]# kubectl get pods 
NAME        READY   STATUS    RESTARTS   AGE
myapp-pod   1/1     Running   0          25m

检测/usr/share/nginx/html/index1.html文件，若文件可以被访问，则让该POD启动，反之一直被探测，直到能被访问为止
[root@k8s-master test]# cat read.yaml 
apiVersion: v1 
kind: Pod 
metadata: 
  name: readiness-httpget-pod 
  namespace: default 
spec: 
  containers: 
  - name: readiness-httpget-container 
    image: wangyanglinux/myapp:v1
    imagePullPolicy: IfNotPresent 	#如果镜像本地存在，不重新下载远程镜像
    readinessProbe: 
      httpGet: 
        port: 80 
        path: /index1.html 
      initialDelaySeconds: 1 	#延迟时间，1秒后启动
      periodSeconds: 3	#3秒后重试，周期时间
	  
创建pod
kubectl apply -f read.yaml 

[root@k8s-master test]# kubectl get pods -w
NAME                    READY   STATUS    RESTARTS   AGE
readiness-httpget-pod   0/1     Running   0          29s

[root@k8s-master ~]# kubectl describe pods readiness-httpget-pod
  Warning  Unhealthy  22s (x21 over 82s)  kubelet            Readiness probe failed: HTTP probe failed with statuscode: 404
 
进入容器创建index1.html检测文件
[root@k8s-master ~]# kubectl exec readiness-httpget-pod -it -- /bin/sh
/ # cd /usr/share/nginx/
/usr/share/nginx # ls
html
/usr/share/nginx # cd html/
/usr/share/nginx/html # ls
50x.html    index.html
/usr/share/nginx/html # echo 1 > index1.html
/usr/share/nginx/html # 

[root@k8s-master test]# kubectl get pods -w
NAME                    READY   STATUS    RESTARTS   AGE
readiness-httpget-pod   1/1     Running   0          4m14s

创建一个文件，60秒后删除，简单来说此POD可以存活60秒后重启，当然不一定是60秒，还有延时时间和重试时间
[root@k8s-master test]# cat live-exec.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: liveness-exec-pod 
  namespace: default
spec: 
  containers: 
  - name: liveness-exec-container 
    image: busybox 
    imagePullPolicy: IfNotPresent 
    command: ["/bin/sh","-c","touch /tmp/live ; sleep 60; rm -rf /tmp/live; sleep 3600"] 
    livenessProbe: 
      exec: 
        command: ["test","-e","/tmp/live"] 
      initialDelaySeconds: 1 
      periodSeconds: 

创建pod
kubectl apply -f live-exec.yaml 

可以看到重启次数，和当前存活多长时间
[root@k8s-master test]# kubectl get pods -w
NAME                READY   STATUS    RESTARTS   AGE
liveness-exec-pod   1/1     Running   0          7s
liveness-exec-pod   1/1     Running   1          100s
liveness-exec-pod   1/1     Running   2          3m19s
liveness-exec-pod   1/1     Running   3          4m58s
liveness-exec-pod   1/1     Running   4          6m37s
liveness-exec-pod   1/1     Running   5          8m16s
liveness-exec-pod   1/1     Running   6          9m55s
liveness-exec-pod   0/1     CrashLoopBackOff   6          11m
liveness-exec-pod   1/1     Running            7          14m
liveness-exec-pod   0/1     CrashLoopBackOff   7          16m

[root@k8s-master test]# cat live-http.yaml 
apiVersion: v1 
kind: Pod 
metadata: 
  name: liveness-httpget-pod 
  namespace: default 
spec:
  containers: 
  - name: liveness-httpget-container 
    image: wangyanglinux/myapp:v1
    imagePullPolicy: IfNotPresent 
    ports: 
    - name: http 
      containerPort: 80 
    livenessProbe: 
      httpGet: 
        port: http 
        path: /index.html 
      initialDelaySeconds: 1 	#延时1秒后监控
      periodSeconds: 3 	#3秒监控一次
      timeoutSeconds: 10 	#延时统计最大延迟时间

创建pods
[root@k8s-master test]# kubectl apply -f live-http.yaml 
pod/liveness-httpget-pod created
[root@k8s-master test]# kubectl get pods
NAME                   READY   STATUS             RESTARTS   AGE
liveness-exec-pod      0/1     CrashLoopBackOff   7          16m
liveness-httpget-pod   1/1     Running            0          3s
[root@k8s-master test]# kubectl get pods -o wide
NAME                   READY   STATUS             RESTARTS   AGE   IP            NODE            NOMINATED NODE   READINESS GATES
liveness-exec-pod      0/1     CrashLoopBackOff   7          16m   10.20.36.72   192.168.10.82   <none>           <none>
liveness-httpget-pod   1/1     Running            0          10s   10.20.36.71   192.168.10.82   <none>           <none>
[root@k8s-master test]# curl 10.20.36.71
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>

[root@k8s-master test]# kubectl exec liveness-httpget-pod -it -- /bin/sh
/ # rm -f /usr/share/nginx/html/index.html

可以看到这里POD已经重启了
[root@k8s-master test]# kubectl get pods
NAME                   READY   STATUS             RESTARTS   AGE
liveness-exec-pod      0/1     CrashLoopBackOff   7          19m
liveness-httpget-pod   1/1     Running            1          2m29s

镜像是80端口，改成8080验证效果
[root@k8s-master test]# cat live-tcp.yaml 
apiVersion: v1 
kind: Pod 
metadata: 
  name: probe-tcp 
spec: 
  containers: 
  - name: nginx 
    image: wangyanglinux/myapp:v1
    livenessProbe: 
      initialDelaySeconds: 5 
      timeoutSeconds: 1 
      tcpSocket: 
        port: 8080
      periodSeconds: 3
	  
创建pods
kubectl apply -f live-tcp.yaml 

可以看到一直重启
[root@k8s-master test]# kubectl get pods -w
NAME        READY   STATUS    RESTARTS   AGE
probe-tcp   1/1     Running   1          16s

删除default名称空间下的POD
kubectl delete pods --all

创建pod
[root@k8s-master test]# kubectl apply -f live-http2.yaml 
pod/liveness-httpget-pod created
可以看到状态是running，但ready还没有准备好
[root@k8s-master test]# kubectl get pods
NAME                   READY   STATUS    RESTARTS   AGE
liveness-httpget-pod   0/1     Running   0          4s
进入POD中的窗口创建index1.html文件
[root@k8s-master test]# kubectl exec liveness-httpget-pod -it -- /bin/sh
/ # cd /usr/share/nginx/html/
/usr/share/nginx/html # ls
50x.html    index.html
/usr/share/nginx/html # echo 1 > index1.html
查看POD ready 已经正常了
[root@k8s-master test]# kubectl get pods
NAME                   READY   STATUS    RESTARTS   AGE
liveness-httpget-pod   1/1     Running   0          55s
在进入容器中删除index.html文件
[root@k8s-master test]# kubectl exec liveness-httpget-pod -it -- rm -f /usr/share/nginx/html/index.html
可以查看到已经重启过POD了
[root@k8s-master test]# kubectl get pods
NAME                   READY   STATUS    RESTARTS   AGE
liveness-httpget-pod   0/1     Running   1          2m44s

[root@k8s-master test]# cat post.yaml 
apiVersion: v1 
kind: Pod
metadata: 
  name: lifecycle-demo 
spec: 
  containers: 
  - name: lifecycle-demo-container 
    image: nginx
    lifecycle: 
      postStart: 
        exec: 
          command: ["/bin/sh", "-c", "echo Hello from the postStart handler > /usr/share/message"] 
      preStop: 
        exec: 
		  #command: ["/usr/sbin/nginx", "-s", "quit"]
          command: ["/bin/sh", "-c", "echo Hello from the postStop handler > /usr/share/message"] 

[root@k8s-master test]# kubectl apply -f post.yaml 
pod/lifecycle-demo created
[root@k8s-master test]# kubectl get pods
NAME             READY   STATUS    RESTARTS   AGE
lifecycle-demo   1/1     Running   0          4s

查看POD中poststart执行没有
[root@k8s-master test]# kubectl exec lifecycle-demo -it -- /bin/bash
root@lifecycle-demo:/# cat /usr/share/message 
Hello from the postStart handler