Directory Ownership in Container: root vs mambauser

[navneethc]

We're attempting to move one of our images from using miniconda3 as the base image to micromamba (1.5-bookworm-slim).

Our repository contains a Makefile that has commands to build the image and run a few tests.

The build is nothing special, and so is the Dockerfile. (We briefly switch to root to install a package using APT.)

The test command is as follows:

docker run --mount type=bind,source="$$(pwd)/test-data",target=/assets --mount type=bind,source="$$(pwd)/test-output",target="/tmp/test-output"  image_name:tag [call to script and arguments omitted]

This eventually fails on my Ubuntu system because the script is not able to write to the /tmp/test-output directory because it is owned by root. However when a colleague runs it on his Mac, the owner of the folder is mambauser and the test runs successfully.

When I explicitly add --user mambauser to the run command, the owner shows up as 1000, but the test still fails.

Short of setting the user to root in the Dockerfile, how can I get this to work?

Happy to share relevant details of Dockerfile, system settings etc., if required.

[wholtz]

Hello @navneethc. I believe what you are seeing is due to a difference in the file permissions on $(pwd)/test-output on the host system.

On the Ubuntu system without using docker, are you able to create a file within /tmp/test-output?

[navneethc]

Hi @wholtz , thanks for the reply. Yes, I can create both the test-output directory and a file within it. Both are owned by the my user. /tmp itself is owned by root, of course. The test-output directory in the host system that I'm trying to mount is within the code repo.

~
❯ mkdir /tmp/test-output

~
❯ touch /tmp/test-output/foo.txt

~
❯ ls -l /tmp/test-output/
total 0
-rw-rw-r-- 1 <username> <username> 0 Nov  7 13:02 foo.txt

~
❯

[wholtz]

Great. Can you try docker run -u "$(id -u):$(id -g)" ... ?

[navneethc]

This worked to the satisfaction of everyone involved. Thank you very much for your help.