this post was submitted on 02 Jan 2024
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Uid/gid in docker containers don't match the uid/gid on the server? (feddit.it)
submitted 10 months ago by [email protected] to c/[email protected]
18 comments fedilink hide all child comments
 

Installed a new debian server, installed docker, but then now i have a problem with permissions on passed directories.

On the previous server, the uid/gids inside the docker container match the uid/gid on the real server.

Root is 0, www-data is 33, and so on.

On this new server, instead, files owned by root (0) in the container are translated to 1000 on the server, www-data (33) is 100032, and so on (+1000 appended to the uid)

Is this normal or did I misconfigure something? On the previous server I was running everything as root (the interactive user was root), and i would like to avoid that

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[–] [email protected] 10 points 10 months ago (3 children)

It's actually a suggested configuration / best practice to NOT have container user IDs matching the host user IDs.

Ditch the idea of root and user in a docker container. For your containerized application use 10000:10001. You'll have only one application and one "user" in the container anyways when doing it right.

To be even more on the secure side use a different random user ID and group ID for every container.

[–] thesmokingman 4 points 10 months ago (1 children)

This is really dependent on whether or not you want to interact with mounted volumes. In a production setting, containers are ephemeral and should essentially never be touched. Data is abstracted into stores like a database or object storage. If you’re interacting with mounted volumes, it’s usually through a different layer of abstraction like Kibana reading Elastic indices. In a self-hosted setting, you might be sidestepping dependency hell on a local system by containerizing. Data is often tightly coupled to the local filesystem. It is much easier to match the container user to the desired local user to avoid constant sudo calls.

I had to check the community before responding. Since we’re talking self-hosted, your advice is largely overkill.

[–] [email protected] 1 points 10 months ago

This is really dependent on […]

… basically anything. Yes. You will always find yourself in problems where the best practice isn’t the best solution for.

In your described use case an option would be having the application inside the container running with 10000:10001 but writing the data into another directory that is configured to use 1000:1001 (or whatever the user is you want to access the data with from your host) and just mount the volume there. This takes a bit more configuration effort than just running the application with 1000:1001 … but still :)

[–] [email protected] 2 points 10 months ago (1 children)

Do I need to actually create the user in advance or can I just choose a string as I see fit?

[–] [email protected] 1 points 10 months ago (1 children)

You don't need to create the user first. Here's the simplest I can come up with:

FROM alpine:latest
COPY myscript.sh /app/myscript.sh
USER 10000:10001
CMD ["sh", "/app/myscript.sh"]

This simply runs /app/myscript.sh with UID 10000 and GID 10001.

[–] [email protected] 1 points 10 months ago (1 children)

Wasnt aware that you can just think of IDs from fresh air.
Thought it was to create the user and ID manually amd then be able to use it.

[–] [email protected] 1 points 10 months ago

Yep! The names are basically just a convenient way for referencing a user or group ID.

Under normal circumstances you should let the system decide what IDs to use, but in the confined environment of a docker container you can do pretty much what you want.

If you really, really, really want to create a user and group just set the IDs manually:

FROM alpine:latest
COPY myscript.sh /app/myscript.sh
RUN addgroup -g 10001 mycoolgroup && adduser -D -u 10000 -G mycoolgroup mycooluser
USER mycooluser:mycoolgroup
CMD ["sh", "/app/myscript.sh"]

Just make sure to stay at or above 10000 so you won't accidentally re-use IDs that are already defined on the host.

[–] [email protected] 1 points 10 months ago* (last edited 10 months ago)

My go-to for user and group IDs is 1234:1234