initContainers

By initializing the container, you can also easily do something similar to poststart

However, it should be clearly distinguished that the target of initializing the container is pod itself, while the target of poststart is container

In most cases, the two methods can be interchanged

apiVersion: v1
kind: Pod
metadata:
  name: init-demo
  labels:
    app: init
spec:
  initContainers:
    - name: init
      image: busybox
      command:
      - wget
      - "-O"
      - "/tmp/index.html"
      - https://studyk8s.com
      volumeMounts:
        - name: initdir
          mountPath: "/tmp"

  containers:
    - name: nginx
      image: nginx
      ports:
      - containerPort: 80
      volumeMounts:
        - name: initdir
          mountPath: /usr/share/nginx/html
  volumes:
    - name: initdir
      emptyDir: {}

The init container is very similar to an ordinary container, except for the following two points:

• Init container always runs to completion (for example, execute WGet, curl, Ping and other commands)
• If there are multiple init containers, the operation must be ended before the next startup

If the init container in the pod fails to start, kubernetes will continue to restart the pod until the init container succeeds. If the restart policy value corresponding to the pod is never (no restart as long as you exit), it will not restart.