Вы не могли бы показать здесь Ваше состояние logind (файлы .service, .socket, конфиги и симлинки), или хотя бы указать, где все это в альтах находится? Я бы сравнил с соседней системой, которая SL 7.95.
Пока только сравнил логи lightdm:
Спойлер
[+0.01s] DEBUG: Logging to /var/log/lightdm/lightdm.log
[+0.01s] DEBUG: Starting Light Display Manager 1.16.7, UID=0 PID=924
[+0.01s] DEBUG: Loading configuration dirs from /usr/share/lightdm/lightdm.conf.d
[+0.01s] DEBUG: Loading configuration dirs from /usr/local/share/lightdm/lightdm.conf.d
[+0.01s] DEBUG: Loading configuration dirs from /etc/xdg/lightdm/lightdm.conf.d
[+0.01s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf
[+0.01s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
[+0.02s] DEBUG: Registered seat module xlocal
[+0.02s] DEBUG: Registered seat module xremote
[+0.02s] DEBUG: Registered seat module unity
[+0.07s] DEBUG: Monitoring logind for seats
[+0.07s] DEBUG: New seat added from logind: seat0
[+0.07s] DEBUG: Seat seat0: Loading properties from config section Seat:*
[+0.07s] DEBUG: Seat seat0: Starting
[+0.07s] DEBUG: Seat seat0: Creating greeter session
[+0.19s] DEBUG: Seat seat0: Creating display server of type x
[+0.20s] DEBUG: Using VT 1
[+0.20s] DEBUG: Seat seat0: Starting local X display on VT 1
[+0.20s] DEBUG: DisplayServer x-0: Logging to /var/log/lightdm/x-0.log
[+0.22s] DEBUG: DisplayServer x-0: Writing X server authority to /var/run/lightdm/root/:0
[+0.22s] DEBUG: DisplayServer x-0: Launching X Server
[+0.22s] DEBUG: Launching process 954: /etc/X11/xinit/xserverrc :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt1 -novtswitch
[+0.22s] DEBUG: DisplayServer x-0: Waiting for ready signal from X server :0
[+0.22s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
[+0.22s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
[+0.25s] WARNING: Error getting user list from org.freedesktop.Accounts: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.Accounts was not provided by any .service files #вот это присутствует и на рабочей машине
[+0.25s] DEBUG: Loading user config from /etc/lightdm/users.conf
[+0.40s] DEBUG: User hasculdr added
[+6.49s] DEBUG: Got signal 10 from process 954
[+6.49s] DEBUG: DisplayServer x-0: Got signal from X server :0
[+6.49s] DEBUG: DisplayServer x-0: Connecting to XServer :0
[+6.49s] DEBUG: Seat seat0: Display server ready, starting session authentication
[+6.49s] DEBUG: Session pid=1178: Started with service 'lightdm-greeter', username '_ldm'
[+6.63s] DEBUG: Session pid=1178: Authentication complete with return value 0: Success
[+6.63s] DEBUG: Seat seat0: Session authenticated, running command
[+6.63s] DEBUG: Session pid=1178: Running command /usr/sbin/lightdm-gtk-greeter
[+6.63s] DEBUG: Creating shared data directory /var/lib/lightdm-data/_ldm
[+6.63s] DEBUG: Session pid=1178: Logging to /var/log/lightdm/x-0-greeter.log
[+6.91s] DEBUG: Activating VT 1
[+6.91s] DEBUG: Activating login1 session c1
[+8.10s] DEBUG: Session pid=1178: Greeter connected version=1.16.7 resettable=false
[+12.62s] DEBUG: Session pid=1178: Greeter start authentication for hasculdr
[+12.62s] DEBUG: Session pid=1204: Started with service 'lightdm', username 'hasculdr'
[+12.88s] DEBUG: Session pid=1204: Got 1 message(s) from PAM
[+12.88s] DEBUG: Session pid=1178: Prompt greeter with 1 message(s)
[+85.52s] DEBUG: Session pid=1178: Continue authentication
[+85.58s] DEBUG: Session pid=1204: Authentication complete with return value 0: Success
[+85.58s] DEBUG: Session pid=1178: Authenticate result for user hasculdr: Success
[+85.58s] DEBUG: Session pid=1178: User hasculdr authorized
[+85.58s] DEBUG: Session pid=1178: Greeter sets language ru_RU.utf8
[+85.69s] DEBUG: Session pid=1178: Greeter requests session default
[+85.69s] DEBUG: Seat seat0: Stopping greeter; display server will be re-used for user session
[+85.69s] DEBUG: Session pid=1178: Sending SIGTERM
[+85.70s] DEBUG: Session pid=1178: Greeter closed communication channel
[+85.70s] DEBUG: Session pid=1178: Exited with return value 0
[+85.70s] DEBUG: Seat seat0: Session stopped
[+85.70s] DEBUG: Seat seat0: Greeter stopped, running session
[+85.70s] DEBUG: Registering session with bus path /org/freedesktop/DisplayManager/Session0
[+85.71s] DEBUG: Session pid=1204: Running command /etc/X11/Xsession default
[+85.71s] DEBUG: Creating shared data directory /var/lib/lightdm-data/hasculdr
[+85.71s] DEBUG: Session pid=1204: Logging to .xsession-errors
[+86.76s] DEBUG: Activating VT 1
[+86.76s] DEBUG: Activating login1 session 2
[+243.57s] DEBUG: Seat seat0 changes active session to вот тут новая сессия, т.к. старая пропадает
[+245.84s] DEBUG: Seat seat0 changes active session to 2
[+245.84s] DEBUG: Session 2 is already active
[+245.88s] DEBUG: Process 954 exited with return value 1
[+245.88s] DEBUG: DisplayServer x-0: X server stopped
[+245.88s] DEBUG: Releasing VT 1
[+245.88s] DEBUG: DisplayServer x-0: Removing X server authority /var/run/lightdm/root/:0
[+245.88s] DEBUG: Seat seat0: Display server stopped
[+245.88s] DEBUG: Seat seat0: Stopping session
[+245.88s] DEBUG: Session pid=1204: Sending SIGTERM
[+245.88s] DEBUG: Seat seat0: Active display server stopped, starting greeter
[+245.88s] DEBUG: Seat seat0: Creating greeter session
[+245.88s] DEBUG: Seat seat0: Creating display server of type x
[+245.88s] DEBUG: Using VT 1
[+245.88s] DEBUG: Seat seat0: Starting local X display on VT 1
[+245.88s] DEBUG: DisplayServer x-0: Logging to /var/log/lightdm/x-0.log
[+245.88s] DEBUG: DisplayServer x-0: Writing X server authority to /var/run/lightdm/root/:0
[+245.88s] DEBUG: DisplayServer x-0: Launching X Server
[+245.88s] DEBUG: Launching process 1922: /etc/X11/xinit/xserverrc :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt1 -novtswitch
[+245.88s] DEBUG: DisplayServer x-0: Waiting for ready signal from X server :0
[+245.89s] DEBUG: Session pid=1204: Exited with return value 0
[+245.89s] DEBUG: Seat seat0: Session stopped
[+245.89s] DEBUG: Seat seat0: Stopping display server, no sessions require it
[+247.04s] DEBUG: Got signal 10 from process 1922
[+247.04s] DEBUG: DisplayServer x-0: Got signal from X server :0
[+247.04s] DEBUG: DisplayServer x-0: Connecting to XServer :0
[+247.04s] DEBUG: Seat seat0: Display server ready, starting session authentication
[+247.04s] DEBUG: Session pid=1928: Started with service 'lightdm-greeter', username '_ldm'
[+247.06s] DEBUG: Session pid=1928: Authentication complete with return value 0: Success
[+247.06s] DEBUG: Seat seat0: Session authenticated, running command
[+247.06s] DEBUG: Session pid=1928: Running command /usr/sbin/lightdm-gtk-greeter
[+247.06s] DEBUG: Creating shared data directory /var/lib/lightdm-data/_ldm
[+247.06s] DEBUG: Session pid=1928: Logging to /var/log/lightdm/x-0-greeter.log
[+247.07s] DEBUG: Activating VT 1
[+247.07s] DEBUG: Activating login1 session c2
[+247.17s] DEBUG: Session pid=1928: Greeter connected version=1.16.7 resettable=false
[+247.39s] DEBUG: Session pid=1928: Greeter start authentication for hasculdr
[+247.39s] DEBUG: Session pid=1947: Started with service 'lightdm', username 'hasculdr'
[+247.40s] DEBUG: Session pid=1947: Got 1 message(s) from PAM
[+247.40s] DEBUG: Session pid=1928: Prompt greeter with 1 message(s)
[+249.93s] DEBUG: Session pid=1928: Continue authentication
[+249.98s] DEBUG: Session pid=1947: Authentication complete with return value 0: Success
[+249.98s] DEBUG: Session pid=1928: Authenticate result for user hasculdr: Success
[+249.98s] DEBUG: Session pid=1928: User hasculdr authorized
[+249.98s] DEBUG: Session pid=1928: Greeter sets language ru_RU.utf8
[+250.13s] DEBUG: Session pid=1928: Greeter requests session default
[+250.13s] DEBUG: Seat seat0: Stopping greeter; display server will be re-used for user session
[+250.13s] DEBUG: Session pid=1928: Sending SIGTERM
[+250.14s] DEBUG: Session pid=1928: Greeter closed communication channel
[+250.14s] DEBUG: Session pid=1928: Exited with return value 0
[+250.14s] DEBUG: Seat seat0: Session stopped
[+250.14s] DEBUG: Seat seat0: Greeter stopped, running session
[+250.14s] DEBUG: Registering session with bus path /org/freedesktop/DisplayManager/Session1
[+250.14s] DEBUG: Session pid=1947: Running command /etc/X11/Xsession default
[+250.14s] DEBUG: Creating shared data directory /var/lib/lightdm-data/hasculdr
[+250.14s] DEBUG: Session pid=1947: Logging to .xsession-errors
[+250.17s] DEBUG: Activating VT 1
[+250.17s] DEBUG: Activating login1 session 4
Опытным путем (номер процесса сменился при падении сессии) выяснил что
[+245.88s] DEBUG: Process 954 exited with return value 1
это
root 1922 2.8 1.5 233652 59448 tty1 Rs+ 09:22 0:26 X -nolisten tcp :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt1 -novtswitch