Bug#769796: systemd: update-rc.d lightdm disable does not work

[Samuel Thibault]

Control: tag -1 - moreinfo

Hello,

> ... which leads me to think that as long as the default DM is lightdm,
> even if one disables the lightdm service, a display-manager service is
> set up and will start. If my guess is correct, then that's a bug in
> lightdm (or in the display-manager logic, perhaps other DMs have the
> same), not in systemd.
> 
> What's the output of these commands?
> 
>   # systemctl status display-manager.service 

● lightdm.service - Light Display Manager
   Loaded: loaded (/lib/systemd/system/lightdm.service; enabled)
   Active: active (running) since dim. 2014-11-16 23:51:12 CET; 55s ago
     Docs: man:lightdm(1)
  Process: 1238 ExecStartPre=/bin/sh -c [ "$(cat /etc/X11/default-display-manager 2>/dev/null)" = "/usr/sbin/lightdm" ] (code=exited, status=0/SUCCESS)
 Main PID: 1245 (lightdm)
   CGroup: /system.slice/lightdm.service
           ├─1245 /usr/sbin/lightdm
           ├─1254 /usr/bin/X :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
           └─2032 lightdm --session-child 12 19

nov. 16 23:51:12 type systemd[1]: Started Light Display Manager.
nov. 16 23:51:14 type lightdm[1946]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)

>   # systemctl status lightdm.service 

● lightdm.service - Light Display Manager
   Loaded: loaded (/lib/systemd/system/lightdm.service; enabled)
   Active: active (running) since dim. 2014-11-16 23:51:12 CET; 1min 5s ago
     Docs: man:lightdm(1)
  Process: 1238 ExecStartPre=/bin/sh -c [ "$(cat /etc/X11/default-display-manager 2>/dev/null)" = "/usr/sbin/lightdm" ] (code=exited, status=0/SUCCESS)
 Main PID: 1245 (lightdm)
   CGroup: /system.slice/lightdm.service
           ├─1245 /usr/sbin/lightdm
           ├─1254 /usr/bin/X :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
           └─2032 lightdm --session-child 12 19

nov. 16 23:51:12 type systemd[1]: Started Light Display Manager.
nov. 16 23:51:14 type lightdm[1946]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)

So it seems they are indeed aliases.  I have run

systemctl disable display-manager

and now lightdm doesn't start any more.

Samuel