K8S之pod入门和Lable

K8S之pod入门和Lable

Pod

• 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

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。

[[email protected] ~]# kubectl get pod -n kube-system 
NAME                                       READY   STATUS    RESTARTS   AGE
calico-kube-controllers-7dbc97f587-c8db6   1/1     Running   2          41h
calico-node-2k8tz                          1/1     Running   2          41h
calico-node-f5dmh                          1/1     Running   2          41h
calico-node-w47xc                          1/1     Running   0          25h
coredns-7ff77c879f-bgxft                   1/1     Running   2          44h
coredns-7ff77c879f-txgpk                   1/1     Running   2          44h
etcd-master                                1/1     Running   2          47h
kube-apiserver-master                      1/1     Running   2          47h
kube-controller-manager-master             1/1     Running   4          47h
kube-proxy-p2qpc                           1/1     Running   2          47h
kube-proxy-p4q77                           1/1     Running   0          25h
kube-proxy-skfq5                           1/1     Running   4          46h
kube-scheduler-master                      1/1     Running   5          47h

Pod操作

• 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

# 命令格式： kubectl run (pod控制器名称) [参数] 
# --image  指定Pod的镜像
# --port   指定端口
# --namespace  指定namespace
[[email protected] ~]# kubectl run nginx --image=nginx:latest --port=80 --namespace dev 
deployment.apps/nginx created

• 查看pod信息

# 查看Pod基本信息
[[email protected] ~]# kubectl get pods -n dev
NAME    READY   STATUS    RESTARTS   AGE
nginx   1/1     Running   0          43s

# 查看Pod的详细信息
[[email protected] ~]# kubectl describe pod nginx -n dev
Name:         nginx
Namespace:    dev
Priority:     0
Node:         node1/192.168.1.105
Start Time:   Wed, 01 Sep 2021 10:29:19 +0800
Labels:       env=test
              version=3.0
Annotations:  cni.projectcalico.org/podIP: 10.244.166.143/32
              cni.projectcalico.org/podIPs: 10.244.166.143/32
Status:       Running
IP:           10.244.166.143
IPs:
  IP:  10.244.166.143
Containers:
  pod:
    Container ID:   docker://ce4bf985af9f01ac31e300becaf47aaf898a60b91936dd09ee1f417f71d34120
    Image:          nginx:latest
    Image ID:       docker-pullable://[email protected]:4d4d96ac750af48c6a551d757c1cbfc071692309b491b70b2b8976e102dd3fef
    Port:           80/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Wed, 01 Sep 2021 10:29:56 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-spd9p (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-spd9p:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-spd9p
    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  Scheduled  15m   default-scheduler  Successfully assigned dev/nginx to node1
  Normal  Pulling    15m   kubelet, node1     Pulling image "nginx:latest"
  Normal  Pulled     14m   kubelet, node1     Successfully pulled image "nginx:latest"
  Normal  Created    14m   kubelet, node1     Created container pod
  Normal  Started    14m   kubelet, node1     Started container pod

• 访问pod，获取pod运行在哪个节点上

# 获取podIP 和 pod 运行在哪个节点上
[[email protected] ~]#  kubectl get pods -n dev -o wide
NAME    READY   STATUS    RESTARTS   AGE   IP               NODE    NOMINATED NODE   READINESS GATES
nginx   1/1     Running   0          16m   10.244.166.143   node1   <none>           <none>
# 访问pod
 [[email protected] ~]# curl   http://10.244.166.143:80
<!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>

• 删除指定pod

[[email protected] ~]# kubectl delete pod nginx -n dev
pod "nginx" deleted

# 此时，显示删除Pod成功，但是再查询，发现又新产生了一个 
[[email protected] ~]# kubectl get pods -n dev
NAME    READY   STATUS    RESTARTS   AGE
nginx   1/1     Running   0          21s

# 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
# 此时要想删除Pod，必须删除Pod控制器

# 先来查询一下当前namespace下的Pod控制器
[[email protected] ~]# kubectl get deploy -n  dev
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   1/1     1            1           9m7s

# 接下来，删除此PodPod控制器
[[email protected] ~]# kubectl delete deploy nginx -n dev
deployment.apps "nginx" deleted

# 稍等片刻，再查询Pod，发现Pod被删除了
[[email protected] ~]# kubectl get pods -n dev
No resources found in dev namespace.

• 基于配置文件的创建

vim pod-nginx.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx
  namespace: dev
spec:
  containers:
  - image: nginx:latest
    name: pod
    ports:
    - name: nginx-port
      containerPort: 80
      protocol: TCP

• 创建：

kubectl create -f pod-nginx.yaml

• 删除：

kubectl delete -f pod-nginx.yaml

Label

• Label 它的作用就是在资源上添加标识，用来对他们进行区分和选择

• Label 会以key=value键值对的形式附加到各种对象上，如Node、pod、Service等

• 一个资源可以定义任意数量的Label，同一个Label也可以被添加到任意数量的资源对象上去

• Label通常在资源定义时确定，当然也可以在对象创建后动态添加或者删除

• 为什么要有Label？

  可以实现分组 namespace 实现的分组是 不同的namespace之间是不同的 适合不同项目的分组 一个项目里面的前端和后端也需要分组 但是还要互通 这个时候就可以通过Label分组。

标签定义完毕之后，还要考虑到标签的选择，这就要使用到 Label Selector

• Label用于给某个资源对象定义标识

• Label Selector 用于查询和筛选拥有某些标签的资源对象

• 两种Label Selector

  基于等式的Label Selector

  name = slave: 选择所有包含Label中key="name"且value="slave"的对象
  
  env != production: 选择所有包括Label中的key="env"且value不等于"production"的对象
  

  基于集合的Label Selector

  - name in (master, slave): 选择所有包含Label中的key="name"且value="master"或"slave"的对象
  
    name not in (frontend): 选择所有包含Label中的key="name"且value不等于"frontend"的对象
  

标签的选择条件可以使用多个，此时将多个Label Selector进行组合，使用逗号","进行分隔即可。例如：

name=slave，env!=production

name not in (frontend)，env!=production

标签操作

• 命令方式

# 为pod资源打标签
[[email protected] ~]# kubectl label pod nginx-pod version=1.0 -n dev
pod/nginx-pod labeled

# 为pod资源更新标签
[[email protected] ~]# kubectl label pod nginx-pod version=2.0 -n dev --overwrite
pod/nginx-pod labeled

# 查看标签
[[email protected] ~]# kubectl get pod nginx-pod  -n dev --show-labels
NAME        READY   STATUS    RESTARTS   AGE   LABELS
nginx-pod   1/1     Running   0          10m   version=2.0

# 筛选标签
[[email protected] ~]# kubectl get pod -n dev -l version=2.0  --show-labels
NAME        READY   STATUS    RESTARTS   AGE   LABELS
nginx-pod   1/1     Running   0          17m   version=2.0
[[email protected] ~]# kubectl get pod -n dev -l version!=2.0 --show-labels
No resources found in dev namespace.

#删除标签
[[email protected] ~]# kubectl label pod nginx-pod version- -n dev
pod/nginx-pod labeled

• 配置文件的方式

apiVersion: v1
kind: Pod
metadata:
  name: nginx
  namespace: dev
  labels:
    version: "3.0" 
    env: "test"
spec:
  containers:
  - image: nginx:latest
    name: pod
    ports:
    - name: nginx-port
      containerPort: 80
      protocol: TCP

执行命令创建kubectl apply -f pod-nginx.yaml

# 查看
[[email protected] ~]# kubectl get pods  -n dev --show-labels 
NAME    READY   STATUS    RESTARTS   AGE   LABELS
nginx   1/1     Running   0          69m   env=test,version=3.0