unable to login using lightdm when then harddisk is full

[Darja]

After login with lightdm with correct credentials, the user session cannot be started with full hdd. Instead of an error message the session is closed immediately and the lightdm login screen is displayed again.

Kubuntu 14.04.2 amd64

The entire system is mounted on /

lightdm is running in classic configuration (requiring the user to type the username and password)

/var/log/lightdm/lightdm.log:

[+24.79s] DEBUG: Session pid=5524: Running command /usr/sbin/lightdm-session /usr/bin/startkde
[+24.79s] DEBUG: Creating shared data directory /var/lib/lightdm-data/darja
[+24.79s] DEBUG: Session pid=5524: Logging to .xsession-errors
[+24.83s] DEBUG: Activating VT 7
[+24.83s] DEBUG: Activating login1 session c30
[+24.85s] DEBUG: Session pid=5524: Exited with return value 1
[+24.85s] DEBUG: Seat: Session stopped
[+24.85s] DEBUG: Seat: Stopping display server, no sessions require it
[+24.85s] DEBUG: Sending signal 15 to process 5482
[+26.78s] DEBUG: Process 5482 exited with return value 0
[+26.78s] DEBUG: DisplayServer x-0: X server stopped
[+26.78s] DEBUG: Releasing VT 7