$ sudo systemd-nspawn -D ./foo
Spawning container mschroot on /opt/foo.
Press ^] three times within 1s to kill container.
root@foo:~# systemctl
Failed to connect to bus: No such file or directory

$ sudo mount --bind /proc /opt/foo/proc
$ sudo chroot /opt/foo/
root@x230:/# systemctl
Running in chroot, ignoring request.