Example of using an init container chown the data in a pvc as a pod starts.

statefulset-chmod.yaml

# Example of using an init container chown the data in a pvc as a pod starts. Useful for migrating
# which user and group your containers run as.

# Works by having an init container mount your data, chmod it before it's consumed by your main container.
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql-statefull
spec:
  podManagementPolicy: OrderedReady
  replicas: 1
  revisionHistoryLimit: 3
  selector:
    matchLabels:
      app: mysql
  serviceName: mysql
  template:
    metadata:
      labels:
        app: mysql
    spec:
      initContainers:
      - name: chowner-mysql-vol-01
        image: registry.hub.docker.com/library/alpine:3.12.0
        # This is where the magic hapens, find files with old UID (1004) and chown with new UID (1005) and GID (2005)
        command: ["find", "/mnt", "-user", "1004", "-group", "2004", "-exec", "chown", "1005:2005", "{}", "+"]
        securityContext:
          readOnlyRootFilesystem: true
          capabilities:
            drop: ["all"]
            add: ["CHOWN"]
          runAsUser: 0
          runAsNonRoot: false
        volumeMounts:
        - name: mysql-vol-01
          mountPath: /mnt
      containers:
      - name: mysql
        env:
          # Use secret in real usage
        - name: MYSQL_ROOT_PASSWORD
          value: password
        image: registry.hub.docker.com/library/mysql:8.0.21
        ports:
        - containerPort: 3306
          name: mysql
          protocol: TCP
        securityContext:
          allowPrivilegeEscalation: false
        volumeMounts:
        - name: mysql-vol-01
          mountPath: /var/lib/mysql
      securityContext:
        runAsUser: 1005
        runAsGroup: 2005
        runAsNonRoot: true
        fsGroup: 3005
      terminationGracePeriodSeconds: 10
  volumeClaimTemplates:
  - apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      name: mysql-vol-01
    spec:
      accessModes:
      - ReadWriteMany
      resources:
        requests:
          storage: 1Gi
      volumeMode: Filesystem