k8s-pod的容器类型

[一、init 容器](#一、init 容器)
[二、pause 容器](#二、pause 容器)
[三、sidecar 容器](#三、sidecar 容器)

一、init 容器

初始化容器像常规应用容器一样，只有一点不同：初始化容器必须在应用容器启动前运行完成

yaml 复制代码

[root@k8s-1 pod]# cat init.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app.kubernetes.io/name: MyApp
spec:
  containers:
  - name: myapp-container
    image: busybox:1.28
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', "until nslookup myservice.$(cat /var/run/secrets/kubernetes.io/serviceaccount/namespace).svc.cluster.local; do echo waiting for myservice; sleep 2; done"]
  - name: init-mydb
    image: busybox:1.28
    command: ['sh', '-c', "until nslookup mydb.$(cat /var/run/secrets/kubernetes.io/serviceaccount/namespace).svc.cluster.local; do echo waiting for mydb; sleep 2; done"]

由于集群中尚未创建 myservice 和 mydb 这两个 Service，导致 nslookup 失败，初始化容器会持续打印 waiting for myservice 并等待

bash 复制代码

[root@k8s-1 pod]# kubectl apply -f init.yaml 
pod/myapp-pod created
[root@k8s-1 pod]# kubectl get pod
NAME                               READY   STATUS      RESTARTS   AGE
myapp-pod                          0/1     Init:0/2    0          6s

创建service

yaml 复制代码

[root@k8s-1 pod]# cat service.yaml 
---
apiVersion: v1
kind: Service
metadata:
  name: myservice
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 9376
---
apiVersion: v1
kind: Service
metadata:
  name: mydb
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 9377
    
[root@k8s-1 pod]# kubectl apply -f service.yaml 
service/myservice created
service/mydb created
[root@k8s-1 pod]# kubectl get services
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP   3d1h
mydb         ClusterIP   10.99.6.65      <none>        80/TCP    18s
myservice    ClusterIP   10.109.68.252   <none>        80/TCP    18s
[root@k8s-1 pod]# kubectl get pod
NAME                               READY   STATUS      RESTARTS   AGE
myapp-pod                          1/1     Running     0          7m2s

初始化容器检测到服务可用后完成初始化，主容器成功启动并进入运行状态

二、pause 容器

Pause 容器（也称为 "Infra 容器"）是每个 Pod 中都会最先创建的一个特殊容器，它不运行任何业务逻辑，而是作为 Pod 中所有容器的 "基础容器"，负责为整个 Pod 提供共享的网络命名空间和 PID 命名空间

docker ps 中可以看到很多的 "/pause"

三、sidecar 容器

像主容器的 "副驾驶"，与主容器共享 Pod 的网络和存储，提供非业务性的辅助功能，且与主容器同时启动、同时退出

yaml 复制代码

[root@k8s-1 pod]# cat sidecar-1.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: counter
spec:
  containers:
  - name: count
    image: busybox:1.28
    args:
    - /bin/sh
    - -c
    - >
      i=0;
      while true;
      do
        echo "$i: $(date)" >> /var/log/1.log;
        echo "$(date) INFO $i" >> /var/log/2.log;
        i=$((i+1));
        sleep 1;
      done      
    volumeMounts:
    - name: varlog
      mountPath: /var/log
  volumes:
  - name: varlog
    emptyDir: {}

创建仅包含主容器的pod

bash 复制代码

[root@k8s-1 pod]# kubectl apply -f sidecar-1.yaml
pod/counter created
[root@k8s-1 pod]# kubectl get pod
NAME                               READY   STATUS      RESTARTS   AGE
counter                            1/1     Running     0          11s
myapp-pod                          1/1     Running     0          21m
# 验证
[root@k8s-1 pod]# kubectl exec -it counter -- sh
/ # cd /var/log
/var/log # ls
1.log  2.log

添加边车容器

yaml 复制代码

[root@k8s-1 pod]# cat sidecar-2.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: counter
spec:
  containers:
  - name: count
    image: busybox:1.28
    args:
    - /bin/sh
    - -c
    - >
      i=0;
      while true;
      do
        echo "$i: $(date)" >> /var/log/1.log;
        echo "$(date) INFO $i" >> /var/log/2.log;
        i=$((i+1));
        sleep 1;
      done      
    volumeMounts:
    - name: varlog
      mountPath: /var/log
  - name: count-log-1
    image: busybox:1.28
    args: [/bin/sh, -c, 'tail -n+1 -F /var/log/1.log']
    volumeMounts:
    - name: varlog
      mountPath: /var/log
  - name: count-log-2
    image: busybox:1.28
    args: [/bin/sh, -c, 'tail -n+1 -F /var/log/2.log']
    volumeMounts:
    - name: varlog
      mountPath: /var/log
  volumes:
  - name: varlog
    emptyDir: {}

验证功能

bash 复制代码

[root@k8s-1 pod]# kubectl apply -f sidecar-2.yaml 
The Pod "counter" is invalid: spec.containers: Forbidden: pod updates may not add or remove containers
[root@k8s-1 pod]# kubectl delete -f sidecar-1.yaml 
pod "counter" deleted
[root@k8s-1 pod]# kubectl apply -f sidecar-2.yaml 
pod/counter created
[root@k8s-1 pod]# kubectl get pod
NAME                               READY   STATUS              RESTARTS   AGE
counter                            3/3     Running             0          28s
myapp-pod                          1/1     Running             0          26m
[root@k8s-1 pod]# kubectl logs counter count-log-1
0: Thu Sep 18 08:52:35 UTC 2025
1: Thu Sep 18 08:52:36 UTC 2025
2: Thu Sep 18 08:52:37 UTC 2025
3: Thu Sep 18 08:52:38 UTC 2025

删除边车容器

删除整个 Pod 后，重新创建不包含该边车容器的新 Pod

或者强制删除

bash 复制代码

[root@k8s-1 pod]#  kubectl delete --grace-period=0 --force  -f sidecar-2.yaml 
warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "counter" force deleted

容器重启策略（restartPolicy）

Always 总是重启：只要容器终止，就自动重启容器
OnFailure 失败时重启：仅当容器异常终止（退出码非 0）时，才重启容器
Never 从不重启：无论容器以何种状态终止，都不重启