004.kubernets对于pod的简单管理

一 pod简介

1.1 介绍

Pod是K8s集群中所有业务类型的基础
Pod是在K8s集群中运行部署应用或服务的最小单元，它是可以支持多容器的。
Pod的设计理念是支持多个容器在一个Pod中共享网络地址和文件系统

pod和容器的区别就是，一个pod可以有多个容器，当一个pod只有一个容器的时候，访问pod就是访问容器，对于一个kubernets来说，一个pods至少有两个容器，一个是不可见的，称为pause容器，另一个就是业务容器

pod是一个逻辑概念，pod中的一个容器异常，整个pod重新创建

Kubernetes为每个Pod都分配了唯一的IP地址，称之为PodIP，一个Pod里的多个容器共享PodIP地址。要求底层网络支持集群内任意两个Pod之间的直接通信，通常采用虚拟二层网络技术来实现（Flannel）。
POD可以与其它主机上的POD直接通讯。
如果有POD意外停止，K8S会根据资源设定重启或创建POD，直到符合预期设定值
pause容器劫持业务容器的所有流量，IP是配置在pause容器的，在创建pod的时候，自动创建，用来接管容器网络

1.2 pod的一个应用场景

pod含有两个容器，File Puller先于web server容器启动
拉取代码放到volume中，然后自毁
web server容器启动，读物volume的代码，用于用户访问

二 POD简单操作

2.1 创建一个关于nginx的pods

[root@docker-server1 namespace]# cd ../

[root@docker-server1 yamls]# mkdir pods

[root@docker-server1 yamls]# cd pods

[root@docker-server1 pods]# vi nginx-pods.yaml

apiVersion: v1

kind: Pod

metadata:

  name: nginx

  labels:

    app: nginx

    annotations:

      test: this is a test app

spec:                 #资源描述信息

  containers:

  - name: nginx

    image: nginx

    ports:

    - containerPort: 80

这是一个最简单的pods，只是运行一个nginx的业务，没有任何其他的东西

[root@docker-server1 pods]# kubectl apply -f nginx-pods.yaml

由于没有指定ns，所以pods运行在defaults中，查看

[root@docker-server1 pods]# kubectl get pods

NAME    READY   STATUS    RESTARTS   AGE

nginx   1/1     Running   0          85s

1/1：后面的1表示这个pods运行了几个容器，前面的1表示几个容器处于redy状态

查看容器

[root@docker-server1 pods]# kubectl get pods -o wide

NAME    READY   STATUS    RESTARTS   AGE     IP           NODE              NOMINATED NODE   READINESS GATES

nginx   1/1     Running   0          6m41s   10.244.2.6   192.168.132.133   <none>           <none>

访问

[root@docker-server1 pods]# curl http://10.244.2.6

<!DOCTYPE html>

<html>

<head>

<title>Welcome to nginx!</title>

<style>

    body {

        width: 35em;

        margin: 0 auto;

        font-family: Tahoma, Verdana, Arial, sans-serif;

    }

</style>

</head>

<body>

<h1>Welcome to nginx!</h1>

<p>If you see this page, the nginx web server is successfully installed and

working. Further configuration is required.</p>

<p>For online documentation and support please refer to

<a href="http://nginx.org/">nginx.org</a>.<br/>

Commercial support is available at

<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>

</body>

</html>

2.2 配置映射端口

[root@docker-server1 pods]# vim nginx-pods.yaml

apiVersion: v1

kind: Pod

metadata:

  name: nginx

  labels:

    app: nginx

spec:

  hostNetwork: true

  containers:

  - name: nginx

    image: nginx

    ports:

    - containerPort: 80

[root@docker-server1 pods]# kubectl delete -f nginx-pods.yaml

[root@docker-server1 pods]# kubectl create -f nginx-pods.yaml

[root@docker-server1 pods]# kubectl get pods -o wide

NAME    READY   STATUS              RESTARTS   AGE   IP                NODE              NOMINATED NODE   READINESS GATES

nginx   0/1     ContainerCreating   0          4s    192.168.132.133   192.168.132.133   <none>           <none>

[root@docker-server1 pods]# kubectl get pods -o wide

NAME    READY   STATUS    RESTARTS   AGE   IP                NODE              NOMINATED NODE   READINESS GATES

nginx   1/1     Running   0          95s   192.168.132.133   192.168.132.133   <none>           <none>

2.3 pod常用配置

name: string

image: string

imagePullPolicy: [Always |Never | IfNotPresent]    #拉取镜像策略，默认是第三种，先看本地，本地没有，才拉取

restartPolicy: [Always | Never | OnFailure]

command: [string]

args: [string]

ports:

containerPort: int

hostPort: int

protocol: string

env:

name: string

value: string

hostNetwork: bool

resources

volumes

livenessProbe

ReadnessProbe

2.4 配置其他策略

运行多个容器，并使用拉取镜像策略

[root@docker-server1 pods]# vim nginx-pods.yaml

apiVersion: v1

kind: Pod

metadata:

  name: nginx

  labels:

    app: nginx

  annotations:

    test: this is a test app

spec:

  imagePullPolicy: Always

  restartPolicy: Always

  containers:

  - name: nginx

    image: nginx

    ports:

    - containerPort: 80

      hostPost: 8080

    env:

    - name: test

      value: aaa

    - name: test1

      value: bbb

  - name: busybox

    image: busybox

    command:

      - sh

      - -c

      - sleep 3600

2.4 删除再创建pod

[root@docker-server1 pods]# kubectl delete pod nginx

[root@docker-server1 pods]# kubectl create -f nginx-pods.yaml

error: error validating "nginx-pods.yaml": error validating data: ValidationError(Pod.spec): unknown field "imagePullPolicy" in io.k8s.api.core.v1.PodSpec; if you choose to ignore these errors, turn validation off with --validate=false

imagePullPolicy这个不能指定所有容器

[root@docker-server1 pods]# vim nginx-pods.yaml

apiVersion: v1

kind: Pod

metadata:

  name: nginx

  labels:

    app: nginx

  annotations:

    test: this is a test app

spec:

  restartPolicy: Always

  containers:

  - name: nginx

    image: nginx

    imagePullPolicy: Always

    ports:

    - containerPort: 80

      hostPort: 8080

    env:

    - name: test

      value: aaa

    - name: test1

      value: bbb

  - name: busybox

    image: busybox

    command:

      - sh

      - -c

      - sleep 3600

[root@docker-server1 pods]# kubectl create -f nginx-pods.yaml

[root@docker-server1 pods]# kubectl get pods

NAME    READY   STATUS    RESTARTS   AGE

nginx   2/2     Running   0          28s

[root@docker-server1 pods]# kubectl get pods -o wide

NAME    READY   STATUS    RESTARTS   AGE   IP           NODE              NOMINATED NODE   READINESS GATES

nginx   2/2     Running   0          36s   10.244.2.7   192.168.132.133   <none>           <none>

做了端口映射，两种方式访问

[root@docker-server1 pods]# curl http://192.168.132.133:8080

[root@docker-server1 pods]# curl http://10.244.2.7

2.5 查看pods的详细信息

[root@docker-server1 pods]# kubectl describe po nginx

Name:         nginx

Namespace:    default

Priority:     0

Node:         192.168.132.133/192.168.132.133

Start Time:   Thu, 09 Jan 2020 18:17:48 -0500

Labels:       app=nginx

Annotations:  test: this is a test app

Status:       Running

IP:           10.244.2.7

IPs:

  IP:  10.244.2.7

Containers:

  nginx:

    Container ID:   docker://676a2d9bebda40d86138190093d1a6d6cf6f16e5ff0e89fc22df53a74bdf8048

    Image:          nginx

    Image ID:       docker-pullable://nginx@sha256:8aa7f6a9585d908a63e5e418dc5d14ae7467d2e36e1ab4f0d8f9d059a3d071ce

    Port:           80/TCP

    Host Port:      8080/TCP

    State:          Running

      Started:      Thu, 09 Jan 2020 18:17:55 -0500

    Ready:          True

    Restart Count:  0

    Environment:

      test:   aaa

      test1:  bbb

    Mounts:

      /var/run/secrets/kubernetes.io/serviceaccount from default-token-bwbrn (ro)

  busybox:

    Container ID:  docker://e8cc006f3ab292701d9876d84881af90f4c97ea22f32bf0cabf2b93d82b8c82b

    Image:         busybox

    Image ID:      docker-pullable://busybox@sha256:6915be4043561d64e0ab0f8f098dc2ac48e077fe23f488ac24b665166898115a

    Port:          <none>

    Host Port:     <none>

    Command:

      sh

      -c

      sleep 3600

    State:          Running

      Started:      Thu, 09 Jan 2020 18:18:00 -0500

    Ready:          True

    Restart Count:  0

    Environment:    <none>

    Mounts:

      /var/run/secrets/kubernetes.io/serviceaccount from default-token-bwbrn (ro)

Conditions:

  Type              Status

  Initialized       True

  Ready             True

  ContainersReady   True

  PodScheduled      True

Volumes:

  default-token-bwbrn:

    Type:        Secret (a volume populated by a Secret)

    SecretName:  default-token-bwbrn

    Optional:    false

QoS Class:       BestEffort

Node-Selectors:  <none>

Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s

                 node.kubernetes.io/unreachable:NoExecute for 300s

Events:

  Type    Reason     Age    From                      Message

  ----    ------     ----   ----                      -------

  Normal  Pulling    4m43s  kubelet, 192.168.132.133  Pulling image "nginx"

  Normal  Scheduled  4m41s  default-scheduler         Successfully assigned default/nginx to 192.168.132.133

  Normal  Pulled     4m38s  kubelet, 192.168.132.133  Successfully pulled image "nginx"

  Normal  Created    4m37s  kubelet, 192.168.132.133  Created container nginx

  Normal  Started    4m37s  kubelet, 192.168.132.133  Started container nginx

  Normal  Pulling    4m37s  kubelet, 192.168.132.133  Pulling image "busybox"

  Normal  Pulled     4m32s  kubelet, 192.168.132.133  Successfully pulled image "busybox"

  Normal  Created    4m32s  kubelet, 192.168.132.133  Created container busybox

  Normal  Started    4m32s  kubelet, 192.168.132.133  Started container busybox

三 yaml文件找回

如果不小心删除了yaml文件，可以通过描述信息找回

3.1 删除yaml文件

[root@docker-server1 pods]# rm -rf nginx-pods.yaml

[root@docker-server1 pods]# kubectl get pods nginx -o yaml

apiVersion: v1

kind: Pod

metadata:

  annotations:

    test: this is a test app

  creationTimestamp: "2020-01-09T23:17:51Z"

  labels:

    app: nginx

  name: nginx

  namespace: default

  resourceVersion: "43864"

  selfLink: /api/v1/namespaces/default/pods/nginx

  uid: 41510342-de97-4b37-ab95-0a01dd73aac7

spec:

  containers:

  - env:

    - name: test

      value: aaa

    - name: test1

      value: bbb

    image: nginx

    imagePullPolicy: Always

    name: nginx

    ports:

    - containerPort: 80

      hostPort: 8080

      protocol: TCP

    resources: {}

    terminationMessagePath: /dev/termination-log

    terminationMessagePolicy: File

    volumeMounts:

    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount

      name: default-token-bwbrn

      readOnly: true

  - command:

    - sh

    - -c

    - sleep 3600

    image: busybox

    imagePullPolicy: Always

    name: busybox

    resources: {}

    terminationMessagePath: /dev/termination-log

    terminationMessagePolicy: File

    volumeMounts:

    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount

      name: default-token-bwbrn

      readOnly: true

  dnsPolicy: ClusterFirst

  enableServiceLinks: true

  nodeName: 192.168.132.133

  priority: 0

  restartPolicy: Always

  schedulerName: default-scheduler

  securityContext: {}

  serviceAccount: default

  serviceAccountName: default

  terminationGracePeriodSeconds: 30

  tolerations:

  - effect: NoExecute

    key: node.kubernetes.io/not-ready

    operator: Exists

    tolerationSeconds: 300

  - effect: NoExecute

    key: node.kubernetes.io/unreachable

    operator: Exists

    tolerationSeconds: 300

  volumes:

  - name: default-token-bwbrn

    secret:

      defaultMode: 420

      secretName: default-token-bwbrn

status:

  conditions:

  - lastProbeTime: null

    lastTransitionTime: "2020-01-09T23:17:48Z"

    status: "True"

    type: Initialized

  - lastProbeTime: null

    lastTransitionTime: "2020-01-09T23:18:01Z"

    status: "True"

    type: Ready

  - lastProbeTime: null

    lastTransitionTime: "2020-01-09T23:18:01Z"

    status: "True"

    type: ContainersReady

  - lastProbeTime: null

    lastTransitionTime: "2020-01-09T23:17:51Z"

    status: "True"

    type: PodScheduled

  containerStatuses:

  - containerID: docker://e8cc006f3ab292701d9876d84881af90f4c97ea22f32bf0cabf2b93d82b8c82b

    image: busybox:latest

    imageID: docker-pullable://busybox@sha256:6915be4043561d64e0ab0f8f098dc2ac48e077fe23f488ac24b665166898115a

    lastState: {}

    name: busybox

    ready: true

    restartCount: 0

    started: true

    state:

      running:

        startedAt: "2020-01-09T23:18:00Z"

  - containerID: docker://676a2d9bebda40d86138190093d1a6d6cf6f16e5ff0e89fc22df53a74bdf8048

    image: nginx:latest

    imageID: docker-pullable://nginx@sha256:8aa7f6a9585d908a63e5e418dc5d14ae7467d2e36e1ab4f0d8f9d059a3d071ce

    lastState: {}

    name: nginx

    ready: true

    restartCount: 0

    started: true

    state:

      running:

        startedAt: "2020-01-09T23:17:55Z"

  hostIP: 192.168.132.133

  phase: Running

  podIP: 10.244.2.7

  podIPs:

  - ip: 10.244.2.7

  qosClass: BestEffort

  startTime: "2020-01-09T23:17:48Z"

3.2 使用命令恢复

[root@docker-server1 pods]# kubectl get pods nginx -o yaml > nginx-pods.yaml

删除不必要的信息

[root@docker-server1 pods]# vim nginx-pods.yaml

apiVersion: v1

kind: Pod

metadata:

  annotations:

    test: this is a test app

  labels:

    app: nginx

  name: nginx

  namespace: default

spec:

  containers:

  - env:

    - name: test

      value: aaa

    - name: test1

      value: bbb

    image: nginx

    imagePullPolicy: Always

    name: nginx

    ports:

    - containerPort: 80

      hostPort: 8080

      protocol: TCP

  - command:

    - sh

    - -c

    - sleep 3600

    image: busybox

    imagePullPolicy: Always

    name: busybox

  restartPolicy: Always

[root@docker-server1 pods]# kubectl delete pod nginx

[root@docker-server1 pods]# kubectl create -f nginx-pods.yaml

3.3 根据恢复的yaml文件验证

[root@docker-server1 pods]# kubectl get pods

NAME    READY   STATUS    RESTARTS   AGE

nginx   2/2     Running   0          14s

[root@docker-server1 pods]# kubectl get pods -o wide

NAME    READY   STATUS    RESTARTS   AGE   IP           NODE              NOMINATED NODE   READINESS GATES

nginx   2/2     Running   0          27s   10.244.2.8   192.168.132.133   <none>           <none>

[root@docker-server1 pods]# curl http://192.168.132.133:8080

[root@docker-server1 pods]# curl http://10.244.2.8

<!DOCTYPE html>

<html>

<head>

<title>Welcome to nginx!</title>

<style>

    body {

        width: 35em;

        margin: 0 auto;

        font-family: Tahoma, Verdana, Arial, sans-serif;

    }

</style>

</head>

<body>

<h1>Welcome to nginx!</h1>

<p>If you see this page, the nginx web server is successfully installed and

working. Further configuration is required.</p>

<p>For online documentation and support please refer to

<a href="http://nginx.org/">nginx.org</a>.<br/>

Commercial support is available at

<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>

</body>

</html>

pod的简单操作学习到这里

博主声明：本文的内容来源主要来自誉天教育晏威老师，由本人实验完成操作验证，需要的博友请联系誉天教育（http://www.yutianedu.com/），获得官方同意或者晏老师（https://www.cnblogs.com/breezey/）本人同意即可转载，谢谢！