Comment # 9 on bug 968042 from Dr. Werner Fink

(In reply to Franck Bui from comment #8)

Indeed the new xdm package has now a native service unit

   /usr/lib/systemd/system/display-manager.service

which then executes the script

   /usr/lib/X11/display-manager

>From the journal log I see
   systemd[1]: samba2.mount mount process exited, code=exited status=32
   systemd[1]: Failed to mount /samba2.
   systemd[1]: Dependency failed for Remote File Systems.
   systemd[1]: Dependency failed for Postfix Mail Transport Agent.
   systemd[1]: Dependency failed for LSB: X Display Manager.
   systemd[1]: Dependency failed for LSB: Network time protocol daemon (ntpd).

The question rises *which* of the dependencies does cause this.  My guess is
the tag `$remote_fs'  and I also guess that the postfix service as well as the
LSB SysVinit scripts for ntpd also require `$remote_fs' aka remote-fs.target. 
Then the problem seems to be the first line which indicates that `Remote File
Systems' aka remote-fs.target does fail.

I'd like to see the output of

  systemctl status remote-fs.target

as well as 

  systemctl list-dependencies --before remote-fs.target

which should include xdm/display-manager and also the output of

  systemctl list-dependencies --after remote-fs.target

to see what is missed ... the only problem is that cut&paste does not
show the colors of the dots (green for loaded /red for not loaded)