Running command:

"systemctl status blarg."
 
Causes systemctl to cease correct operation. Trying a valid unit name with '.' appended also triggers the issue:

root@CS6c15f9abcdef:~# systemctl status rsyslog.
Failed to issue method call: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.

From then on any systemctl command will fail:

root@CS6c15f9abcdef:~# systemctl
Failed to get D-Bus connection: Failed to connect to socket /run/systemd/private: Connection refused
root@CS6c15f9abcdef:~# systemctl status rsyslog
Failed to get D-Bus connection: Failed to connect to socket /run/systemd/private: Connection refused

Reboot will also fail:

root@CS6c15f9abcdef:/# reboot
Failed to open /dev/initctl: No such device or address
Failed to talk to init daemon.


But systemd process still appears to be running:

root@CS6c15f9abcdef:~# ps -A | grep systemd
    1 ?        00:00:06 systemd
   65 ?        00:00:00 systemd-udevd
   73 ?        00:00:03 systemd-journal
  107 ?        00:00:00 systemd-logind

The version of systemd we are running is 195:

root@CS6c15f9abcdef:~# systemctl --version
systemd 195
debian
-PAM -LIBWRAP -AUDIT -SELINUX +IMA +SYSVINIT -LIBCRYPTSETUP +GCRYPT +ACL +XZ

The version of linux is:
Linux CS6c15f9abcdef 3.5.0 #1 PREEMPT Mon Aug 19 14:55:29 BST 2013 armv7l GNU/Linux

This kernel has been built using yocto.

This is not a problem for us, it was only discovered accidentally after a typo. If further details are required please explain what is required although note that the fault produces no dmesg output and the system the problem has been observed on does not have a syslog.