K8S实践Ⅱ（K8S之Pod）

Posted 2021-12-14

一、Static Pod

静态Pod是由kubectl进行管理的仅存于特定Node上的Pod。其不能通过API Server进行管理，无法与ReplicationController、Deployment或者DaemonSet进行关联，并且kubelet也无法对他们进行健康检查。静态Pod总是由kubectl进行创建，并且总是在kubelet所在的Node上运行。
创建静态 Pod 有两种方式：配置文件和 HTTP 两种方式

由kubeadm安装的集群，对应的kubelet已经配置了静态Pod文件的路径

# cat /var/lib/kubelet/config.yaml |grep staticPodPath
staticPodPath: /etc/kubernetes/manifests

1.配置一个静态Pod的yaml文件放入该路径

# cat static-web.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    name: static-web
spec:
  containers:
  - name: static-web
    image: nginx
    ports:
    - name: web
      containerPort: 80

2.查看docker进程

# docker ps 
CONTAINER ID        IMAGE                   COMMAND                  CREATED             STATUS              PORTS               NAMES
b682d21563dd        nginx                   "nginx -g ‘daemon of…"   6 minutes ago       Up 6 minutes                            k8s_static-web_static-web-k8s-2_default_a850d62a685464dd2c0bdb31222085c9_0

3.查看Pod创建情况

# kubectl get pod
NAME               READY   STATUS    RESTARTS   AGE
static-web-k8s-2   1/1     Running   0          7m14s

4.尝试删除该静态Pod

[[email protected] chapter1]# kubectl delete pod static-web-k8s-2
pod "static-web-k8s-2" deleted
[[email protected] chapter1]# kubectl get pod
NAME               READY   STATUS    RESTARTS   AGE
static-web-k8s-2   0/1     Pending   0          1s
[[email protected] chapter1]# kubectl get pod
NAME               READY   STATUS    RESTARTS   AGE
static-web-k8s-2   0/1     Pending   0          4s
[[email protected] chapter1]# kubectl get pod
NAME               READY   STATUS    RESTARTS   AGE
static-web-k8s-2   1/1     Running   0          6s

5.删除/etc/kubernetes/manifests下的yaml文件

# kubectl get pod
No resources found.

二、Pod容器共享Volume

同一个Pod里面的多个容器能够共享Pod级别的存储卷Volume，Volume可以被定义为各种类型，多个容器各自进行挂载操作，进行数据共享。

配置yaml文件

apiVersion: v1
kind: Pod
metadata:
  name: volume-pod
spec:
  containers:
  - name: tomcat
    image: tomcat
    ports:
    - containerPort: 8080
    volumeMounts:
    - name: app-logs
      mountPath: /usr/local/tomcat/logs
  - name: busybox
    image: busybox
    command: ["sh", "-c", "tail -f /logs/catalina*.log"]
    volumeMounts:
    - name: app-logs
      mountPath: /logs
  volumes:
  - name: app-logs
    emptyDir: 

创建pod

# kubectl apply -f pod-volume-logs.yaml 
pod/volume-pod created

# kubectl get pod
NAME         READY   STATUS    RESTARTS   AGE
volume-pod   2/2     Running   0          4m42s

pod中有两个容器，一个是tomcat用于写入日志文件，另一个busybox用于读日志文件

# kubectl logs volume-pod -c busybox
31-May-2019 16:54:39.573 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/docs] has finished in [26] ms
31-May-2019 16:54:39.573 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/examples]
31-May-2019 16:54:39.954 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/examples] has finished in [380] ms
31-May-2019 16:54:39.954 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/host-manager]
31-May-2019 16:54:39.992 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/host-manager] has finished in [38] ms
31-May-2019 16:54:39.992 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/manager]
31-May-2019 16:54:40.025 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/manager] has finished in [32] ms
31-May-2019 16:54:40.031 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["http-nio-8080"]
31-May-2019 16:54:40.045 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["ajp-nio-8009"]
31-May-2019 16:54:40.093 INFO [main] org.apache.catalina.startup.Catalina.start Server startup in 992 ms

# kubectl exec -it volume-pod -c tomcat -- ls /usr/local/tomcat/logs
catalina.2019-05-31.log      localhost_access_log.2019-05-31.txt
host-manager.2019-05-31.log  manager.2019-05-31.log
localhost.2019-05-31.log
# kubectl exec -it volume-pod -c tomcat -- tail /usr/local/tomcat/logs/catalina.2019-05-31.log
31-May-2019 16:54:39.573 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/docs] has finished in [26] ms
31-May-2019 16:54:39.573 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/examples]
31-May-2019 16:54:39.954 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/examples] has finished in [380] ms
31-May-2019 16:54:39.954 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/host-manager]
31-May-2019 16:54:39.992 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/host-manager] has finished in [38] ms
31-May-2019 16:54:39.992 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/manager]
31-May-2019 16:54:40.025 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/manager] has finished in [32] ms
31-May-2019 16:54:40.031 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["http-nio-8080"]
31-May-2019 16:54:40.045 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["ajp-nio-8009"]
31-May-2019 16:54:40.093 INFO [main] org.apache.catalina.startup.Catalina.start Server startup in 992 ms

三、Pod的应用配置管理ConfigMap