Run systemctl inside docker container
It seems there are some things that need a bit of clearing up.
Normally, when you run a container you aren’t running an init system (like systemd). The PID 1 of a Docker container should instead be the "entrypoint", the command that were used to launch the container.
If the entrypoint process no longer runs, the container goes down with it.
However, it seems that there is a Debian port with systemd enabled, but I haven't tried this myself.