Container running as UID 0 despite named volume being owned by other user

[PaddyTheShamrock]

Issue

If I pre-create a named volume as per your instructions:

docker run --rm -v minecraft:/data alpine chown 1100:1100 /data

and then docker-compose up, the volume permissions are changed back to root, and the demoter matches to UID=0, running the container as root.

I've confirmed that the chown is working ok, and the permissions are correct on the filesystem before docker-compose up is run:

ls -aln /var/lib/docker/volumes/minecraft/ drwxr-xr-x 14 1100 1100 4096 Jan 28 13:40 _data

But afterwards, they've been changed to UID/GID 0. I assume the volume is having its permissions changed to suit the initial docker user (root) before the demotion happens.

Fix

I've found that by touching a file in the named volume first, and then running the chown on the whole folder, everything works as expected and the container runs as GID 1100:

docker run --rm -v minecraft:/data alpine sh -c "touch /data/.initialised && chown -R 1100:1100 /data"

[itzg]

Great discovery! Now that you say that I vaguely remembering a solution like that with pre-populating volumes in a Dockerfile.

I'll see if that's something that can be automated by the startup script when the initial user is root and UID/GID differ from the directory ownership.