How to mount the directory with a specific user?

General Discussions
1

Basically I have this postgres image:

1   FROM postgres:latest
  1 COPY deployment/postgres_init /docker-entrypoint-initdb.d
  2 USER 999
  3 RUN initdb
  4 CMD postgres -c hba_file=docker-entrypoint-initdb.d/pg_hba.conf -c config_fi    le=docker-entrypoint-initdb.d/postgresql.conf

and this postgres deployment with volumeMount:

1   apiVersion: apps/v1
  1 kind: Deployment
  2 metadata:
  3   name: postgres-deployment
  4 spec:
  5   replicas: 1
  6   selector:
  7     matchLabels:
  8       component: postgres
  9   template:
 10     metadata:
 11       labels:
 12         component: postgres
 13     spec:
 14       securityContext:
 15         runAsUser: 999
 16       volumes:
 17         - name: postgres-storage
 18           persistentVolumeClaim:
 19             claimName: postgres-persistent-volume-claim
 20       containers:
 21         - name: postgres
 22           image: prikshet/postgres
 23           ports:
 24             - containerPort: 5432
 25           volumeMounts:
 26             - name: postgres-storage
 27               mountPath: /var/lib/postgresql/data
 28               subPath: postgres
 29           imagePullPolicy: Always

When I remove volumeMount there’s no error, but if I add volumeMount then I get the following:

2021-08-10 15:07:33.911 GMT [9] LOG:  skipping missing configuration file "/var/lib/postgresql/data/postgresql.auto.conf"
2021-08-10 15:07:33.911 UTC [9] FATAL:  data directory "/var/lib/postgresql/data" has wrong ownership
2021-08-10 15:07:33.911 UTC [9] HINT:  The server must be started by the user that owns the data directory.

You’d think that runAsUser: 999 in the yaml and USER 999 in the dockerfile would work, but it doesn’t. How to fix this?