Find all code on Github [stretch](https://github.com/jochumdev/proxmox-dockerfiles/tree/master/stretch-systemd) and [buster](https://github.com/jochumdev/proxmox-dockerfiles/tree/master/buster-systemd).
so i tried systemd from [stretch-backports](https://github.com/jochumdev/proxmox-dockerfiles/blob/master/stretch-systemd/Dockerfile#L18) 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:
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](https://docs.gitlab.com/runner/executors/docker.html#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**: