Kubernetes - setting custom permissions/file ownership per volume (and not per pod)

Question

Is there any way to set per-volume permissions/ownership in Kubernetes declaratively?

Usecase:

• a pod is composed of two containers, running as two distinct users/groups, both of them non-root, and are unable to sudo
• the containers mount a volume each, and need to create files in these volumes (e.g. both of them want to write logs)

We know that we can use fsGroup, however that is a pod-level declaration. So even if we pick fsGroup equal to user in first container, then we are going to have permission issues in the other one. (ref: Kubernetes: how to set VolumeMount user group and file permissions)

Answer 1

One solution is to use init-container to change permissions of mounted directories.

The init-container would need to mount both volumes (from both containers), and do the needed chown/chmod operations.

Drawbacks:

• extra container that needs to be aware of other containers' specific (ie. uid/gid)
• init container needs to run as root to perform chown

Answer 2

It can be done with adding one init container with root access.

    initContainers:
    - name: changeowner
      image: busybox
      command: ["sh", "-c", "chown -R 200:200 /<volume>"]   
      volumeMounts:
      - name: <your volume>
        mountPath: /<volume>