--userns=auto - Cannot find mappings for user "root"

[Perdition-117]

Hi,

I'm currently exploring podman and discovered the --userns=auto option, which seems very useful while running as root. I don't really know how to get it working, however.

# podman run --userns=auto docker.io/library/busybox
ERRO[0000] Cannot find mappings for user "root": no subuid ranges found for user "root" in /etc/subuid
Error: creating container storage: not enough unused IDs in user namespace

I feel like using mappings for root is a bad idea, but according to the documentation, it should look for mappings for a user named containers. I don't know what that is about, but I don't have such a user. I tried just creating such a user and adding mappings for it, but it still looks for root mappings.

I use podman 5.4.2 installed from the Debian repository.

[eriksjolund]

The error seems to come from this source code line

podman/vendor/github.com/containers/storage/userns.go

Line 49 in be85287

logrus.Errorf("Cannot find mappings for user %q: %v", username, err)

The username root might come from this line

podman/vendor/github.com/containers/storage/userns.go

Line 45 in be85287

username = RootAutoUserNsUser

Did you set

root-auto-userns-user = "root"

in the file storage.conf
?

For details about root-auto-userns-user, see
https://github.com/containers/container-libs/blob/397182c71d26098acb693a7a4571ed96935484b3/storage/storage.conf#L108

The theory above is not very probable, but no one replied so this reply might be better than nothing.