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When trying to log onto a Kubuntu 14.04 LTS system. I noticed that all users would pass, when logging in via ssh, but graphical login (i.e. LightDM with the KDE greeter) would just be possible for local accounts.

More precise: LDAP users would be authenticated with ease, but then KDE Plasma would not start up. The relevant lines of the log file:

# /var/log/lightdm/lightdm.log
DEBUG: Seat: Failed to find session configuration default
DEBUG: Seat: Can't find session 'default'

The lines do not show up when local accounts log in.

How to fix this? Explanations?

arney
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2 Answers2

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You probably did not set the user-session in LightDM's config file, e.g.

# /etc/lightdm/lightdm.conf
[SeatDefaults]
user-session=plasma-kde
...

therefore LightDM looks into the user's ~/.dmrc file and finds

Session=default

and hence looks for /usr/share/xsessions/default.desktop which is missing.

arney
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  • Changing /etc/lightdm/lightdm.conf did not fix it for me, but modifying ~/.dmrc did the trick. Isn't ~/.dmrc prioritary over the /etc/ configuration? – Elouan Keryell-Even Jan 14 '19 at 16:20
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sure, thread is pretty old - but anyway: stumbled over this thread, when trying to fix lightdm not starting on a bananapi M3 (armbian) - solution was to apt install lightdm-gtk-greeter (which was not pulled in when installing lightdm) maybe this helps someone :)

lgkf
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  • Upgrading linux mint to v20 found your solution . greeter was absent , ended up installing slick-greeter as lightdm-gtk-greeter looked not so slick, but anyway , thank you very much , the answer ended my frustration. – Sergey Sep 24 '20 at 11:28
  • thanks for sharing. I wonder what's the oldest answer from SO that are still actively found and used now... :-) – Billy Oct 08 '20 at 22:09