this post was submitted on 02 Oct 2025
23 points (100.0% liked)

Selfhosted

52037 readers
776 users here now

A place to share alternatives to popular online services that can be self-hosted without giving up privacy or locking you into a service you don't control.

Rules:

  1. Be civil: we're here to support and learn from one another. Insults won't be tolerated. Flame wars are frowned upon.

  2. No spam posting.

  3. Posts have to be centered around self-hosting. There are other communities for discussing hardware or home computing. If it's not obvious why your post topic revolves around selfhosting, please include details to make it clear.

  4. Don't duplicate the full text of your blog or github here. Just post the link for folks to click.

  5. Submission headline should match the article title (don’t cherry-pick information from the title to fit your agenda).

  6. No trolling.

Resources:

Any issues on the community? Report it using the report flag.

Questions? DM the mods!

founded 2 years ago
MODERATORS
 

I am moving from Docker to rootless podman and one thing that's surprising to me is that podman can create files that my user is, seemingly, not allowed to even read, so I need root to backup them.

For example, this one created by the postgres service of immich:

-rw-------. 1 525286 525286 1.6K Oct 2 20:16 /var/home/railcar/immich/postgres/pg_stat_tmp/global.stat

Is this expected in general (not for immich in particular)? Is there a single solution to solve this of does it have to be built in the images? It really feels wrong that I can start a container that will create files I am not allowed to even read.

you are viewing a single comment's thread
view the rest of the comments
[–] InnerScientist@lemmy.world 5 points 3 days ago

It is expected, the users inside the container are "real" users. They just get offset inside the container and some mapping is applied:

Root inside the container is mapped outside to the user running the container, everything that has the owner "root" inside the container can be read from outside the container as your user.

Everything that is saved as non-root inside the container gets mapped to the first subuid in /etc/subuids for your user + the uid inside the container.

You can change this mapping such that, for example, user 1000 inside the container gets mapped to your user outside the container.

An example:

You have a postgres database inside a container with a volume for the database files. The postgres process inside the container doesn't run as root but instead runs as uid 100 as such it also saves its files with that user.
If you look at the volume outside the container you will get a permission denied error because it is owned by user 100100 (subuids starts at 100000 and usid inside container is 100).

To fix: Either run your inner processes as root, this can often be done using environment variables and has almost no security impact or add --userns keep-id:uid=100,gid=100 to the cmdline to make uid 100 inside the container map to your user instead of root (this creates a new image automatically and takes a while on the first run)