gitlab-runner docker with debian systemd
An howto on systemd with a Debian stretch/buster docker container and Gitlab.
This didn’t work at all with systemd from Debian stretch, but as i knew from my LXD experience systemd in stretch is buggy with containers, so i tried systemd from stretch-backports which worked well.
Now to have systemd finaly working in a stretch container you need to mount a tmpfs into /run and /run/lock else systemd tries to mount those - fails with permission denied and freezes.
Also you need to bind-mount cgroups into the stretch container (doing that as “volume”).
This is the full line to run a Debian 9 container with systemd from backports:
docker run -d -it --mount type=tmpfs,destination=/run --mount type=tmpfs,destination=/run/lock -v /sys/fs/cgroup:/sys/fs/cgroup:ro <image>
It’s same as with stretch but no backports.
Gitlab-runner for both
Ok, so we found out that we need:
- a tmpfs /run
- a tmpfs /run/lock
- cgroup bind-mount
gitlab-runner does volumes which means the bind-mount is easy to solve, but what about the tmpfs mounts?
After a while a found a feature they call Mounting a directory in RAM, which is nothing else than a mount of a tmpfs :)
This means we need to add the following to /etc/gitlab-runner/config.toml:
[runners.docker] volumes = ["/sys/fs/cgroup:/sys/fs/cgroup:ro", "/cache"] [runners.docker.services_tmpfs] "/run" = "rw" "/run/lock" = "rw"
Easy, isn’t it?