title: Kubernetes fsGroup not changing file ownership on PersistentVolume
body: <p>On the host, everything in the mounted directory (<code>/opt/testpod</code>) is owned by uid=0 gid=0. I need those files to be owned by whatever the container decides, i.e. a different gid, to be able to write there. Resources I'm testing with:</p>
  <pre><code>---
  apiVersion: v1
  kind: PersistentVolume
  metadata:
    name: pv
    labels:
      name: pv
  spec:
    storageClassName: manual
    capacity:
      storage: 10Mi
    accessModes:
      - ReadWriteOnce
    hostPath:
      path: &quot;/opt/testpod&quot;
  
  ---
  apiVersion: v1
  kind: PersistentVolumeClaim
  metadata:
    name: pvc
  spec:
    storageClassName: manual
    selector:
      matchLabels:
        name: pv
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: 10Mi
  
  ---
  apiVersion: v1
  kind: Pod
  metadata:
    name: testpod
  spec:
    nodeSelector:
      foo: bar
    securityContext:
      runAsUser: 500
      runAsGroup: 500
      fsGroup: 500
    volumes:
    - name: vol
      persistentVolumeClaim:
        claimName: pvc
    containers:
    - name: testpod
      image: busybox
      command: [ &quot;sh&quot;, &quot;-c&quot;, &quot;sleep 1h&quot; ]
      volumeMounts:
      - name: vol
        mountPath: /data
  </code></pre>
  <p>After the pod is running, I <code>kubectl exec</code> into it and <code>ls -la /data</code> shows everything still owned by gid=0. According to some Kuber docs, <code>fsGroup</code> is supposed to chown everything on the pod start but it doesn't happen. What am I doing wrong please?</p>