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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?

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up vote 1 down vote accepted

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.

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