whoa - you have a container with working systemd ? I thought that was an unfixed bug - https://github.com/docker/docker/pull/5773 and https://github.com/docker/docker/issues/3629
[vlisivka@apollo5 docker-centos7-systemd-unpriv]$ ./enter.sh
[root@e3c3dd7539ad /]# ps ax
PID TTY STAT TIME COMMAND
1 ? Ss 0:00 /usr/lib/systemd/systemd
71 ? Ss 0:00 /usr/lib/systemd/systemd-journald
74 ? Ss 0:00 bash
92 ? R+ 0:00 ps ax
https://github.com/vlisivka/docker-centos7-systemd-unpriv