Postgres on Azure kubernetes volume permission error

Question

I'm trying to deploy Postgresql on Azure Kube.netes with data persistency. So I'm using PVC. I searched lots of posts on here, most of them offered yaml files like below, but it's giving the error below;

chmod: changing permissions of '/var/lib/postgresql/data/pgdata': Operation not permitted
The files belonging to this database system will be owned by user "postgres".
This user must also own the server process.

The database cluster will be initialized with locale "en_US.utf8".
The default database encoding has accordingly been set to "UTF8".
The default text search configuration will be set to "english".

Data page checksums are disabled.

initdb: error: could not change permissions of directory "/var/lib/postgresql/data/pgdata": Operation not permitted
fixing permissions on existing directory /var/lib/postgresql/data/pgdata ...

deployment yaml file is below;

apiVersion: apps/v1
kind: Deployment
metadata:
  name: postgresql
spec:
  replicas: 1
  selector:
    matchLabels:
      app: postgresql
  template:
    metadata:
      labels:
        app: postgresql
    spec:
      containers:
        - name: postgresql
          image: postgres:13.2
          securityContext:
            runAsUser: 999
          imagePullPolicy: "IfNotPresent"
          ports:
            - containerPort: 5432
          envFrom:
            - secretRef:
                name: postgresql-secret
          volumeMounts:
            - mountPath: /var/lib/postgresql/data
              name: postgredb-kap
      volumes:
        - name: postgredb-kap
          persistentVolumeClaim:
            claimName: postgresql-pvc

Secret yaml is below;

apiVersion: v1
kind: Secret
metadata:
  name: postgresql-secret
type: Opaque
data:
  POSTGRES_DB: a2V5sd4=
  POSTGRES_USER: cG9zdGdyZXNhZG1pbg==
  POSTGRES_PASSWORD: c234Rw==
  PGDATA: L3Za234dGF0YQ==

pvc and sc yaml files are below:

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: postgresql-pvc
  labels:
    app: postgresql
spec:
  storageClassName: postgresql-sc
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
---
allowVolumeExpansion: true
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: postgresql-sc
mountOptions:
- dir_mode=0777
- file_mode=0777
- uid=1000
- gid=1000
parameters:
  skuName: Standard_LRS
provisioner: kubernetes.io/azure-file
reclaimPolicy: Retain

So when I use the mountpath like " - mountPath: /var/lib/postgresql/ ", it's working. I can reach the DB and it's good. But when I delete the pod and recreating, there is no DB. So no data persistency.

Can you please help, what am I missing here?

Thanks!

Answer 1

One thing you could try is to change uid=1000,gid=1000 in mount options to 999 since this is the uid of postgres user in postgres conatiner (I didn't test this).

---

Another solution that will for certain solve this issue involves init conatainers.

Postgres container requires to start as root to be able to chown pgdata dir since its mounted as root dir. After it does this, it drops root permisions and runs as postgres user.

But you can use init container (running as root) to chmod the volume dir so that you can run main container as non-root.

Here is an example:

  initContainers:
    - name: init
      image: alpine
      command: ["sh", "-c", "chown 999:999 /var/lib/postgresql/data"]
      volumeMounts:
        - mountPath: /var/lib/postgresql/data
          name: postgredb-kap

Answer 2

Based on the helpful answer from Matt. For bitnami postgresql the initContainer also works but with a slightly different configuration:

      initContainers:
        - name: init
          image: alpine
          command: ["sh", "-c", "chown 1001:1001 /bitnami/postgresql"]
          volumeMounts:
            - mountPath: /bitnami/postgresql
              name: postgres-volume