Kubernetes Pod

POD

定义

Pod 是可以在 Kubernetes 中创建和管理的、最小的可部署的计算单元，每个Pod包含了一个pause容器，pause容器时Pod的父容器，负责僵尸进程的回收管理，通过pause容器可以支持同一个Pod里面的多个容器共享存储、网络、ipc等。

说明：Pod一般不直接操作，通过 Deployment、StatefulSet、DaemonSet控制。

[root@master01 ~]# kubectl get pod -n kube-system -owide
NAME                                       READY   STATUS    RESTARTS   AGE    IP               NODE       NOMINATED NODE   READINESS GATES
calico-kube-controllers-5f6d4b864b-k45q5   1/1     Running   4          4d9h   192.168.44.13    node01     <none>           <none>
calico-node-58hbg                          1/1     Running   4          4d9h   192.168.44.12    master03   <none>           <none>
calico-node-dlj65                          1/1     Running   3          4d9h   192.168.44.11    master02   <none>           <none>
calico-node-jqb6h                          1/1     Running   4          4d9h   192.168.44.14    node02     <none>           <none>
calico-node-r8fl5                          1/1     Running   5          4d9h   192.168.44.10    master01   <none>           <none>
calico-node-wv4vx                          1/1     Running   4          4d9h   192.168.44.13    node01     <none>           <none>
coredns-867d46bfc6-ljdjr                   1/1     Running   4          4d9h   172.29.55.5      node01     <none>           <none>
metrics-server-595f65d8d5-6k4wq            1/1     Running   6          4d9h   172.21.231.133   node02     <none>           <none>
[root@master01 ~]#  docker ps
CONTAINER ID   IMAGE                                                                 COMMAND         CREATED       STATUS       PORTS     NAMES
b6b4384467b1   d45bf977dfbf                                                          "start_runit"   2 hours ago   Up 2 hours             k8s_calico-node_calico-node-r8fl5_kube-system_e06be2e7-75dc-4029-b468-f3b7f253ab44_5
683c51344750   registry.cn-hangzhou.aliyuncs.com/google_containers/pause-amd64:3.2   "/pause"        2 hours ago   Up 2 hours             k8s_POD_calico-node-r8fl5_kube-system_e06be2e7-75dc-4029-b468-f3b7f253ab44_5

使用Pod

创建一个pod
vim pod.yaml

apiVersion: v1 
kind: Pod      
metadata:       
  name: nginx   
  labels:      
    app: nginx
    role: frontend 
  annotations: 
    app: nginx
spec:  
  containers:  
  - name: nginx 
    image: nginx
    imagePullPolicy: IfNotPresent
    command: 
    - nginx 
    - -g
    - "daemon off;"
    workingDir: /usr/share/nginx/html       
    ports:  
    - name: http    
      containerPort: 80     
      protocol: TCP 
    env:   
    - name: TZ      
      value: Asia/Shanghai
    - name: LANG
      value: en_US.utf8
  restartPolicy: Always

[root@master01 pod_demo]# kubectl create -f pod.yaml
pod/nginx created

[root@master01 pod_demo]# kubectl get po
NAME    READY   STATUS              RESTARTS   AGE
nginx   0/1     ContainerCreating   0          13s

[root@master01 pod_demo]# kubectl get po --show-labels
NAME    READY   STATUS              RESTARTS   AGE   LABELS
nginx   0/1     ContainerCreating   0          30s   app=nginx,role=frontend

[root@master01 pod_demo]# kubectl create -f pod.yaml -n kube-public
pod/nginx created
[root@master01 pod_demo]# kubectl get po -n kube-public
NAME    READY   STATUS              RESTARTS   AGE
nginx   0/1     ContainerCreating   0          12s

#如果pod在命名空间下已存在 再次创建回报错
[root@master01 pod_demo]# kubectl create -f pod.yaml -n kube-public
Error from server (AlreadyExists): error when creating "pod.yaml": pods "nginx" already exists

# 修改配置使用apply命令
[root@master01 pod_demo]#  vim pod.yaml
[root@master01 pod_demo]# kubectl apply -f pod.yaml -n kube-public
pod/nginx configured