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?

2 Answers 2


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

# /etc/lightdm/lightdm.conf

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


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

  • 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? Jan 14, 2019 at 16:20

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 :)

  • 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, 2020 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 8, 2020 at 22:09

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