Pod 是 kubernetes 集群进行管理的最小单元，程序要运行必须部署在容器中，而容器必须存在于 Pod 中。Pod 可以认为是容器的封装，一个 Pod 中可以存在一个或者多个容器。
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    kubernetes 在集群启动之后，集群中的各个组件也都是以 Pod 方式运行的。可以通过下面命令查看：

    1. [root@master ~]# kubectl get pod -n kube-system
    2. NAMESPACE     NAME                             READY   STATUS    RESTARTS   AGE
    3. kube-system   coredns-6955765f44-68g6v         1/1     Running   0          2d1h
    4. kube-system   coredns-6955765f44-cs5r8         1/1     Running   0          2d1h
    5. kube-system   etcd-master                      1/1     Running   0          2d1h
    6. kube-system   kube-apiserver-master            1/1     Running   0          2d1h
    7. kube-system   kube-controller-manager-master   1/1     Running   0          2d1h
    8. kube-system   kube-flannel-ds-amd64-47r25      1/1     Running   0          2d1h
    9. kube-system   kube-flannel-ds-amd64-ls5lh      1/1     Running   0          2d1h
    10. kube-system   kube-proxy-685tk                 1/1     Running   0          2d1h
    11. kube-system   kube-proxy-87spt                 1/1     Running   0          2d1h
    12. kube-system   kube-scheduler-master            1/1     Running   0          2d1h

    创建并运行
    kubernetes 没有提供单独运行 Pod 的命令，都是通过 Pod 控制器来实现的

    1. # 命令格式： kubectl run (pod控制器名称) [参数] 
    2. # --image  指定Pod的镜像
    3. # --port   指定端口
    4. # --namespace  指定namespace
    5. [root@master ~]# kubectl run nginx --image=nginx:1.17.1 --port=80 --namespace dev 
    6. deployment.apps/nginx created

    查看 pod 信息

    1. # 查看Pod基本信息
    2. [root@master ~]# kubectl get pods -n dev
    3. NAME                     READY   STATUS    RESTARTS   AGE
    4. nginx-5ff7956ff6-fg2db   1/1     Running   0          43s
    6. # 查看Pod的详细信息
    7. [root@master ~]# kubectl describe pod nginx-5ff7956ff6-fg2db -n dev
    8. Name:         nginx-5ff7956ff6-fg2db
    9. Namespace:    dev
    10. Priority:     0
    11. Node:         node1/192.168.109.101
    12. Start Time:   Wed, 08 Apr 2020 09:29:24 +0800
    13. Labels:       pod-template-hash=5ff7956ff6
    14.               run=nginx
    15. Annotations:  <none>
    16. Status:       Running
    17. IP:           10.244.1.23
    18. IPs:
    19.   IP:           10.244.1.23
    20. Controlled By:  ReplicaSet/nginx-5ff7956ff6
    21. Containers:
    22.   nginx:
    23.     Container ID:   docker://4c62b8c0648d2512380f4ffa5da2c99d16e05634979973449c98e9b829f6253c
    24.     Image:          nginx:1.17.1
    25.     Image ID:       docker-pullable://nginx@sha256:485b610fefec7ff6c463ced9623314a04ed67e3945b9c08d7e53a47f6d108dc7
    26.     Port:           80/TCP
    27.     Host Port:      0/TCP
    28.     State:          Running
    29.       Started:      Wed, 08 Apr 2020 09:30:01 +0800
    30.     Ready:          True
    31.     Restart Count:  0
    32.     Environment:    <none>
    33.     Mounts:
    34.       /var/run/secrets/kubernetes.io/serviceaccount from default-token-hwvvw (ro)
    35. Conditions:
    36.   Type              Status
    37.   Initialized       True
    38.   Ready             True
    39.   ContainersReady   True
    40.   PodScheduled      True
    41. Volumes:
    42.   default-token-hwvvw:
    43.     Type:        Secret (a volume populated by a Secret)
    44.     SecretName:  default-token-hwvvw
    45.     Optional:    false
    46. QoS Class:       BestEffort
    47. Node-Selectors:  <none>
    48. Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
    49.                  node.kubernetes.io/unreachable:NoExecute for 300s
    50. Events:
    51.   Type    Reason     Age        From               Message
    52.   ----    ------     ----       ----               -------
    53.   Normal  Scheduled  <unknown>  default-scheduler  Successfully assigned dev/nginx-5ff7956ff6-fg2db to node1
    54.   Normal  Pulling    4m11s      kubelet, node1     Pulling image "nginx:1.17.1"
    55.   Normal  Pulled     3m36s      kubelet, node1     Successfully pulled image "nginx:1.17.1"
    56.   Normal  Created    3m36s      kubelet, node1     Created container nginx
    57.   Normal  Started    3m36s      kubelet, node1     Started container nginx

    访问 Pod

    1. # 获取podIP
    2. [root@master ~]# kubectl get pods -n dev -o wide
    3. NAME                     READY   STATUS    RESTARTS   AGE    IP             NODE    ... 
    4. nginx-5ff7956ff6-fg2db   1/1     Running   0          190s   10.244.1.23   node1   ...
    6. #访问POD
    7. [root@master ~]# curl http://10.244.1.23:80
    8. <!DOCTYPE html>
    9. <html>
    10. <head>
    11.     <title>Welcome to nginx!</title>
    12. </head>
    13. <body>
    14.     <p><em>Thank you for using nginx.</em></p>
    15. </body>
    16. </html>

    删除指定 Pod

    1. # 删除指定Pod
    2. [root@master ~]# kubectl delete pod nginx-5ff7956ff6-fg2db -n dev
    3. pod "nginx-5ff7956ff6-fg2db" deleted
    5. # 此时，显示删除Pod成功，但是再查询，发现又新产生了一个 
    6. [root@master ~]# kubectl get pods -n dev
    7. NAME                     READY   STATUS    RESTARTS   AGE
    8. nginx-5ff7956ff6-jj4ng   1/1     Running   0          21s
    10. # 这是因为当前Pod是由Pod控制器创建的，控制器会监控Pod状况，一旦发现Pod死亡，会立即重建
    11. # 此时要想删除Pod，必须删除Pod控制器
    13. # 先来查询一下当前namespace下的Pod控制器
    14. [root@master ~]# kubectl get deploy -n  dev
    15. NAME    READY   UP-TO-DATE   AVAILABLE   AGE
    16. nginx   1/1     1            1           9m7s
    18. # 接下来，删除此PodPod控制器
    19. [root@master ~]# kubectl delete deploy nginx -n dev
    20. deployment.apps "nginx" deleted
    22. # 稍等片刻，再查询Pod，发现Pod被删除了
    23. [root@master ~]# kubectl get pods -n dev
    24. No resources found in dev namespace.

    image.png
    配置操作
    创建一个 pod-nginx.yaml，内容如下：

    1. apiVersion: v1
    2. kind: Pod
    3. metadata:
    4.   name: nginx
    5.   namespace: dev
    6. spec:
    7.   containers:
    8.   - image: nginx:1.17.1
    9.     name: pod
    10.     ports:
    11.     - name: nginx-port
    12.       containerPort: 80
    13.       protocol: TCP

    然后就可以执行对应的创建和删除命令了：
    创建：kubectl create -f pod-nginx.yaml
    删除：kubectl delete -f pod-nginx.yaml