[Pkg-xfce-devel] Bug#844295: Bug#844295: [lightdm] "FAILED to start Light Desktop Manager" errors after dpkg-reconfigure lightdm and choosing another desktop manager

[Laura Arjona Reina]

Hi Yves-Alexis

El 14/11/16 a las 10:25, Yves-Alexis Perez escribió:
> On Mon, 2016-11-14 at 08:37 +0100, Laura Arjona Reina wrote:
>> dpkg-reconfigure lightdm
>>
>> and chose "kdm" as my default desktop manager, just to try kdm.
>>
>> Then when I boot the PC, I get "FAILED to start light display manager"
>> errors.
>> If I do dpkg-reconfigure lightdm and I choose lightdm again, the errors
>> disappear.
>>
>> I guess the service is not correctly disabled when I choose a different
>> desktop manager.
>>
>> If I should report this bug against a different package, please tell.
>
> Hi Laura, thanks for the report. Here are few questions:
>
> - does it happen when you install and select another display manager?

I've installed gdm and it does not happen, it seems it happens only with 
kdm (it does not happen with sddm either).

> - do you use sysvrc or systemd as init?

systemd

> - when you select kdm, what is the content of /etc/X11/default-display-
> manager?

With lightdm:

cat /etc/X11/default-display-manager
/usr/sbin/lightdm


With kdm:

/usr/bin/kdm


when I do

sudo dpkg-reconfigure lightdm and select kdm, I get this error:

ERROR: /lib/systemd/system/kdm.service is the selected default display 
manager but does not exist

> - where does /etc/systemd/system/display-manager.service symlink points to?

with lightdm:

/etc/systemd/system/display-manager.service -> 
/lib/systemd/system/lightdm.service

with kdm:

/etc/systemd/system/display-manager.service -> 
/lib/systemd/system/lightdm.service

> - what does systemctl status display-manager return?

With lightdm

● lightdm.service - Light Display Manager
    Loaded: loaded (/lib/systemd/system/lightdm.service; enabled; ve
    Active: active (running) since lun 2016-11-14 13:19:57 CET; 1h 2
      Docs: man:lightdm(1)
   Process: 874 ExecStartPre=/bin/sh -c [ "$(cat /etc/X11/default-di
  Main PID: 877 (lightdm)
     Tasks: 5 (limit: 4915)
    CGroup: /system.slice/lightdm.service
            ├─877 /usr/sbin/lightdm
            └─936 /usr/lib/xorg/Xorg :0 -seat seat0 -auth /var/run/l
lines 1-10/10 (END)

with kdm

● lightdm.service - Light Display Manager
    Loaded: loaded (/lib/systemd/system/lightdm.service; enabled; vendor 
preset: enabled)
    Active: failed (Result: start-limit-hit) since lun 2016-11-14 
14:43:05 CET; 29min ago
      Docs: man:lightdm(1)
   Process: 914 ExecStartPre=/bin/sh -c [ "$(cat 
/etc/X11/default-display-manager 2>/dev/null)" = "/usr/sbin/lightdm" ] 
(code=exited, status=1/FAILURE)


> - what does systemctl status lightdm return?
with lightdm
● lightdm.service - Light Display Manager
    Loaded: loaded (/lib/systemd/system/lightdm.service; enabled; ve
    Active: active (running) since lun 2016-11-14 13:19:57 CET; 1h 1
      Docs: man:lightdm(1)
   Process: 874 ExecStartPre=/bin/sh -c [ "$(cat /etc/X11/default-di
  Main PID: 877 (lightdm)
     Tasks: 5 (limit: 4915)
    CGroup: /system.slice/lightdm.service
            ├─877 /usr/sbin/lightdm
            └─936 /usr/lib/xorg/Xorg :0 -seat seat0 -auth /var/run/l
lines 1-10/10 (END)

with kdm

● lightdm.service - Light Display Manager
    Loaded: loaded (/lib/systemd/system/lightdm.service; enabled; vendor 
preset: enabled)
    Active: failed (Result: start-limit-hit) since lun 2016-11-14 
14:43:05 CET; 30min ago
      Docs: man:lightdm(1)
   Process: 914 ExecStartPre=/bin/sh -c [ "$(cat 
/etc/X11/default-display-manager 2>/dev/null)" = "/usr/sbin/lightdm" ] 
(code=exited, status=1/FAILURE)

> - what does systemctl status kdm return?

with lightdm

● kdm.service - LSB: X display manager for KDE
    Loaded: loaded (/etc/init.d/kdm; generated; vendor preset: enabl
    Active: active (exited) since lun 2016-11-14 13:19:52 CET; 1h 18
      Docs: man:systemd-sysv-generator(8)
     Tasks: 0 (limit: 4915)
    CGroup: /system.slice/kdm.service

● gdm.service - GNOME Display Manager
    Loaded: loaded (/lib/systemd/system/gdm.service; static; vendor
    Active: inactive (dead)

with kdm

● kdm.service - LSB: X display manager for KDE
    Loaded: loaded (/etc/init.d/kdm; generated; vendor preset: enabled)
    Active: active (running) since lun 2016-11-14 14:42:58 CET; 30min ago
      Docs: man:systemd-sysv-generator(8)
   Process: 724 ExecStart=/etc/init.d/kdm start (code=exited, 
status=0/SUCCESS)
     Tasks: 3 (limit: 4915)
    CGroup: /system.slice/kdm.service
            ├─793 /usr/bin/kdm
            └─795 /usr/lib/xorg/Xorg :0 vt7 -br -nolisten tcp -auth 
/var/run/xauth/A:0-8AixAa

● gdm.service - GNOME Display Manager
    Loaded: loaded (/lib/systemd/system/gdm.service; static; vendor 
preset: enabled)
    Active: inactive (dead)

>
> The way to select the default display manager is not completely intuitive so
> there might be bugs there, but it was working just fine before so I'm a bit
> puzzled (the implementation comes from gdm+kdm as far as I remember).
>

Answering the questions you proposed, I've realised that the problem is 
not related to lightdm, it's related with kdm. Because the same problem 
happens when I switch from sddm to kdm 
(/etc/systemd/system/display-manager.service still points to sddm 
instead of pointing to kdm), and it does not happen when I switch from 
lightdm to sddm.

I'm not sure which is the better step to do now, though: reasigning this 
bug report to kdm? or closing this and creating a new bug report against 
kdm?

Best regards

-- 
Laura Arjona Reina
https://wiki.debian.org/LauraArjona