Systemd guix containers: unable to execute Permission denied

[Edouard Klein <edou@rdklein.fr>]

Hi,

I'm running a container using a systemd unit. This unit calls a script
that call guix system container and calls the returned script.

When I launch this script by itself, everything works as expected.

When I launch this script with systemd, I can launch any command except
as root in the container.

For example, once I get a shell in the container with guix container
exec, I can do:
sudo -u nginx echo toto

And it will succeed when the container is launched by hand, but failed
when launched with systemd.

Any idea, even far fetched, will be appreciated. I have a burning hatred
for systemd (not my choice) that this incident is fueling.

I've tried everything I could think of:
- activating and deactivating various systemd flags
- changing the uid of nginx to match a user on the host system
- changing the uid of nginx to avoid matching a user on the host system
- stopping nscd on the container,

etc.

I'm looking into other means of achieving what I want, but this SHOULD
work, and it WOULD if it wasn't for effing systemd.

Cheers,

Edouard.