Can not write to SMB/CIFS mounted Docker volume

[noveb]

Hi everyone,

I have a setup with the handbrake container on one VM and a SMB/CIFS server on another VM. I created 2 CIFS volumes in Docker and mount them to /storage and /output. Sadly I get this error
[autovideoconverter] ERROR: Cannot process watch folder '/watch', because the associated output directory '/output' is not writable.

I already tried some things: if I make the volume read-only, this will fail on startup
[cont-init ] 55-handbrake.sh: executing... [cont-init ] 55-handbrake.sh: core dump file location: core [cont-init ] 55-handbrake.sh: core dump file size: unlimited (blocks) [cont-init ] 55-handbrake.sh: terminated successfully.

I can also exec into the handbrake container and do touch myfile and mkdir mydir in /output without problems.

Does anyone have an idea what I am missing and what the problem is?
Greetings

[jlesage]

How did you create the container and how did you create the CIFS volumes ? There is probably a mismatch between the user of the container (specified via USER_ID and GROUP_ID) and the user of the mounted CIFS volumes.

[noveb]

I use Portainer as UI but basically i did this https://docs.docker.com/storage/volumes/#create-cifssamba-volumes

When i exec into the container, I am the root user and can write to the volume. So I guess there is then something up with permissions? I thought this kind of volume would hide the underlying user & auth stuff from the container. User ID on the smb server is 1004 but that does not even exist on the docker host. I am a bit clueless now :D

[jlesage]

Inside the container, you can do ls -l /storage to see user/group associate to the files/folders. You should probably re-use the same.
It's not a problem if this user/group doesn't exists on the Docker host.