Kubernetes - 尝试创建带有初始化容器的Pod

Question

我尝试使用初始化Pods。我想要使用init container创建文件，然后使用默认容器来检查文件是否存在并暂停一段时间。

我的yaml如下：

apiVersion: v1
kind: Pod
metadata:
  name: init-test-pod
spec:
  containers:
  - name: myapp-container
    image: alpine
    command: ['sh', '-c', 'if [ -e /workdir/test.txt ]; then sleep 99999; fi']
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', 'mkdir /workdir; echo>/workdir/test.txt']

当我尝试从alpine镜像进行调试时，我使用以下命令创建：

kubectl run alpine --rm -ti --image=alpine /bin/sh

If you don't see a command prompt, try pressing enter.
/ # if [ -e /workdir/test.txt ]; then sleep 3; fi
/ # mkdir /workdir; echo>/workdir/test.txt
/ # if [ -e /workdir/test.txt ]; then sleep 3; fi
/ *here shell sleeps for 3 seconds
/ #

看起来命令已经按预期运行。

但是在我的真正的k8s集群上，主容器只有CrashLoopBackOff。

kubectl describe pod init-test-pod

只显示了这个错误：

Containers:
  myapp-container:
    Container ID:  docker://xxx
    Image:         alpine
    Image ID:      docker-pullable://alpine@sha256:xxx
    Port:          <none>
    Host Port:     <none>
    Command:
      sh
      -c
      if [ -e /workdir/test.txt ]; then sleep 99999; fi
    State:          Waiting
      Reason:       CrashLoopBackOff
    Last State:     Terminated
      Reason:       Completed
      Exit Code:    0
    Ready:          False
    Restart Count:  3
    Environment:    <none>

- golang

Answer 1

这里的问题是你的主容器无法找到你创建的文件夹。当初始容器运行完成时，文件夹也会被清除。你需要使用持久化存储卷才能在两个容器之间共享文件夹：

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: mypvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi
---
apiVersion: v1
kind: Pod
metadata:
  name: init-test-pod
spec:
  volumes:
  - name: mypvc
    persistentVolumeClaim:
      claimName: mypvc
  containers:
  - name: myapp-container
    image: alpine
    command: ['sh', '-c', 'if [ -f /workdir/test.txt ]; then sleep 99999; fi']
    volumeMounts:
    - name: mypvc
      mountPath: /workdir
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', 'mkdir /workdir; echo>/workdir/test.txt']
    volumeMounts:
    - name: mypvc
      mountPath: /workdir

你也可以查看emptyDir，这样你就不需要使用PVC：

apiVersion: v1
kind: Pod
metadata:
  name: init-test-pod
spec:
  volumes:
  - name: mydir
    emptyDir: {}
  containers:
  - name: myapp-container
    image: alpine
    command: ['sh', '-c', 'if [ -f /workdir/test.txt ]; then sleep 99999; fi']
    volumeMounts:
    - name: mydir
      mountPath: /workdir
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', 'mkdir /workdir; echo>/workdir/test.txt']
    volumeMounts:
    - name: mydir
      mountPath: /workdir

- cookiedough

---

您也可以使用Emptydir来实现相同的结果，而无需持久化文件。 - Suresh Vishnoi

Answer 2

这是因为您的两个容器拥有不同的文件系统。您需要使用一个emptyDir卷共享此文件：

apiVersion: v1
kind: Pod
metadata:
  name: init-test-pod
spec:
  containers:
  - name: myapp-container
    image: alpine
    command: ['sh', '-c', 'if [ -e /workdir/test.txt ]; then sleep 99999; fi']
    volumeMounts:
    - mountPath: /workdir
      name: workdir
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', 'mkdir /workdir; echo>/workdir/test.txt']
    volumeMounts:
    - mountPath: /workdir
      name: workdir
  volumes:
  - name: workdir
    emptyDir: {}

- Grigory Ignatyev