Hi, I've just upgraded my x86_64 laptop to Ubuntu 17.10, and I believe I'm hitting the same problem. In short, I can't login from the lightdm greeter: it accepts my password, the login process starts and immediately stops and comes back to the lightdm greeter. It worked well before I upgraded.... I had warnings about pam-kwallet.so, which I "solved" by installing libpam-kwallet and libpam-kwallet5 packages, and manually created /lib/security symlink pointing to /lib/x86_64-linux-gnu/security. This fixed the warnings, but not the login problem :( The next thing I noticed is the error message mentioned in this bug report. My /var/log/lightdm/lightdm.log file contains: [+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log [+0.01s] DEBUG: Starting Light Display Manager 1.24.0, UID=0 PID=1208 [+0.01s] DEBUG: Loading configuration dirs from /usr/share/lightdm/lightdm.conf.d [+0.01s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-disable-guest.conf [+0.01s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-disable-log-backup.conf [+0.01s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-greeter-wrapper.conf [+0.01s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-guest-wrapper.conf [+0.01s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-unity-greeter.conf [+0.01s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-xserver-command.conf [+0.01s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-lightdm-gtk-greeter.conf [+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.d/10-xubuntu.conf [+0.01s] DEBUG: [SeatDefaults] is now called [Seat:*], please update this configuration [+0.01s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf [+0.01s] DEBUG: [SeatDefaults] is now called [Seat:*], please update this configuration [+0.01s] DEBUG: Registered seat module local [+0.01s] DEBUG: Registered seat module xremote [+0.01s] DEBUG: Registered seat module unity [+0.01s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager [+0.20s] DEBUG: Monitoring logind for seats [+0.20s] DEBUG: New seat added from logind: seat0 [+0.20s] DEBUG: Seat seat0: Loading properties from config section Seat:* [+0.20s] DEBUG: Seat seat0: Starting [+0.20s] DEBUG: Seat seat0: Creating greeter session [+0.20s] DEBUG: Seat seat0: Creating display server of type x [+0.20s] DEBUG: Seat seat0: Plymouth is running on VT 1, but this is less than the configured minimum of 7 so not replacing it [+0.20s] DEBUG: Quitting Plymouth [+0.34s] DEBUG: Using VT 7 [+0.34s] DEBUG: Seat seat0: Starting local X display on VT 7 [+0.34s] DEBUG: XServer 0: Logging to /var/log/lightdm/x-0.log [+0.34s] DEBUG: XServer 0: Writing X server authority to /var/run/lightdm/root/:0 [+0.34s] DEBUG: XServer 0: Launching X Server [+0.34s] DEBUG: Launching process 1296: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch [+0.34s] DEBUG: XServer 0: Waiting for ready signal from X server :0 [+0.34s] DEBUG: Acquired bus name org.freedesktop.DisplayManager [+0.34s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0 [+0.35s] DEBUG: Loading users from org.freedesktop.Accounts [+0.35s] DEBUG: User /org/freedesktop/Accounts/User1001 added [+0.36s] DEBUG: User /org/freedesktop/Accounts/User1027 added [+1.32s] DEBUG: Got signal 10 from process 1296 [+1.32s] DEBUG: XServer 0: Got signal from X server :0 [+1.32s] DEBUG: XServer 0: Connecting to XServer :0 [+2.21s] CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed [+2.21s] DEBUG: Seat seat0: Display server ready, starting session authentication [+2.21s] DEBUG: Session pid=1362: Started with service 'lightdm-greeter', username 'lightdm' [+2.23s] DEBUG: Session pid=1362: Authentication complete with return value 0: Success [+2.23s] DEBUG: Seat seat0: Session authenticated, running command [+2.23s] DEBUG: Session pid=1362: Running command /usr/lib/lightdm/lightdm-greeter-session /usr/sbin/lightdm-gtk-greeter [+2.23s] DEBUG: Creating shared data directory /var/lib/lightdm-data/lightdm [+2.23s] DEBUG: Session pid=1362: Logging to /var/log/lightdm/seat0-greeter.log [+2.29s] DEBUG: Activating VT 7 [+2.29s] DEBUG: Activating login1 session c1 [+2.29s] DEBUG: Seat seat0 changes active session to c1 [+2.29s] DEBUG: Session c1 is already active [+2.49s] DEBUG: Greeter connected version=1.24.0 api=1 resettable=false [+2.83s] DEBUG: Greeter start authentication for lyon [+2.83s] DEBUG: Session pid=1422: Started with service 'lightdm', username 'lyon' [+2.84s] DEBUG: Session pid=1422: Got 1 message(s) from PAM [+2.84s] DEBUG: Prompt greeter with 1 message(s) [+11.59s] DEBUG: Continue authentication [+11.76s] DEBUG: Session pid=1422: Authentication complete with return value 0: Success [+11.76s] DEBUG: Authenticate result for user lyon: Success [+11.76s] DEBUG: User lyon authorized [+11.77s] DEBUG: Greeter sets language en_US [+11.78s] DEBUG: Greeter requests session xfce [+11.78s] DEBUG: Seat seat0: Stopping greeter; display server will be re-used for user session [+11.78s] DEBUG: Terminating login1 session c1 [+11.79s] DEBUG: Session pid=1362: Sending SIGTERM [+11.79s] DEBUG: Session pid=1362: Exited with return value 0 [+11.79s] DEBUG: Seat seat0: Session stopped [+11.79s] DEBUG: Seat seat0: Greeter stopped, running session [+11.79s] DEBUG: Registering session with bus path /org/freedesktop/DisplayManager/Session0 [+11.79s] CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed [+11.79s] DEBUG: Session pid=1422: Running command /usr/sbin/lightdm-session startxfce4 [+11.79s] DEBUG: Creating shared data directory /var/lib/lightdm-data/lyon [+11.79s] DEBUG: Session pid=1422: Logging to .xsession-errors [+11.85s] DEBUG: Activating VT 7 [+11.85s] DEBUG: Activating login1 session c2 [+11.85s] DEBUG: Seat seat0 changes active session to c2 [+11.85s] DEBUG: Session c2 is already active [+12.14s] DEBUG: Session pid=1422: Exited with return value 127 [+12.14s] DEBUG: Seat seat0: Session stopped [+12.14s] DEBUG: Seat seat0: Stopping display server, no sessions require it [+12.14s] DEBUG: Sending signal 15 to process 1296 [+12.15s] DEBUG: Seat seat0 changes active session to [+13.24s] DEBUG: Process 1296 exited with return value 0 [+13.24s] DEBUG: XServer 0: X server stopped [+13.24s] DEBUG: Releasing VT 7 [+13.24s] DEBUG: XServer 0: Removing X server authority /var/run/lightdm/root/:0 [+13.24s] DEBUG: Seat seat0: Display server stopped [+13.24s] DEBUG: Seat seat0: Active display server stopped, starting greeter [+13.24s] DEBUG: Seat seat0: Creating greeter session [+13.24s] DEBUG: Seat seat0: Creating display server of type x [+13.24s] DEBUG: Using VT 7 [+13.24s] DEBUG: Seat seat0: Starting local X display on VT 7 [+13.24s] DEBUG: XServer 0: Logging to /var/log/lightdm/x-0.log [+13.24s] DEBUG: XServer 0: Writing X server authority to /var/run/lightdm/root/:0 [+13.24s] DEBUG: XServer 0: Launching X Server [+13.24s] DEBUG: Launching process 1671: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch [+13.24s] DEBUG: XServer 0: Waiting for ready signal from X server :0 [+14.22s] DEBUG: Got signal 10 from process 1671 [+14.22s] DEBUG: XServer 0: Got signal from X server :0 [+14.22s] DEBUG: XServer 0: Connecting to XServer :0 [+15.09s] CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed [+15.09s] DEBUG: Seat seat0: Display server ready, starting session authentication [+15.09s] DEBUG: Session pid=1675: Started with service 'lightdm-greeter', username 'lightdm' [+15.11s] DEBUG: Session pid=1675: Authentication complete with return value 0: Success [+15.11s] DEBUG: Seat seat0: Session authenticated, running command [+15.11s] DEBUG: Session pid=1675: Running command /usr/lib/lightdm/lightdm-greeter-session /usr/sbin/lightdm-gtk-greeter [+15.12s] DEBUG: Creating shared data directory /var/lib/lightdm-data/lightdm [+15.12s] DEBUG: Session pid=1675: Logging to /var/log/lightdm/seat0-greeter.log [+15.17s] DEBUG: Activating VT 7 [+15.17s] DEBUG: Activating login1 session c3 [+15.17s] DEBUG: Seat seat0 changes active session to c3 [+15.17s] DEBUG: Session c3 is already active [+15.26s] DEBUG: Greeter connected version=1.24.0 api=1 resettable=false [+15.47s] DEBUG: Greeter start authentication for lyon [+15.47s] DEBUG: Session pid=1731: Started with service 'lightdm', username 'lyon' [+15.48s] DEBUG: Session pid=1731: Got 1 message(s) from PAM [+15.48s] DEBUG: Prompt greeter with 1 message(s) [+21.07s] DEBUG: Seat seat0 changes active session to [+28.35s] DEBUG: Seat seat0 changes active session to 4 [+200.49s] DEBUG: Seat seat0 changes active session to [+200.50s] DEBUG: Seat seat0 changes active session to 4 [+202.02s] DEBUG: Seat seat0 changes active session to c3 [+202.02s] DEBUG: Session c3 is already active [+206.07s] DEBUG: Continue authentication [+206.23s] DEBUG: Session pid=1731: Authentication complete with return value 0: Success [+206.23s] DEBUG: Authenticate result for user lyon: Success [+206.23s] DEBUG: User lyon authorized [+206.23s] DEBUG: Greeter sets language en_US [+206.24s] DEBUG: Greeter requests session xfce [+206.25s] DEBUG: Seat seat0: Stopping greeter; display server will be re-used for user session [+206.25s] DEBUG: Terminating login1 session c3 [+206.25s] DEBUG: Session pid=1675: Sending SIGTERM [+206.25s] DEBUG: Session pid=1675: Exited with return value 0 [+206.25s] DEBUG: Seat seat0: Session stopped [+206.25s] DEBUG: Seat seat0: Greeter stopped, running session [+206.25s] DEBUG: Registering session with bus path /org/freedesktop/DisplayManager/Session1 [+206.26s] CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed [+206.26s] DEBUG: Session pid=1731: Running command /usr/sbin/lightdm-session startxfce4 [+206.26s] DEBUG: Creating shared data directory /var/lib/lightdm-data/lyon [+206.26s] DEBUG: Session pid=1731: Logging to .xsession-errors [+206.29s] DEBUG: Activating VT 7 [+206.29s] DEBUG: Activating login1 session c4 [+206.29s] DEBUG: Seat seat0 changes active session to c4 [+206.29s] DEBUG: Session c4 is already active [+206.42s] DEBUG: Session pid=1731: Exited with return value 127 [+206.42s] DEBUG: Seat seat0: Session stopped [+206.42s] DEBUG: Seat seat0: Stopping display server, no sessions require it [+206.42s] DEBUG: Sending signal 15 to process 1671 [+206.44s] DEBUG: Seat seat0 changes active session to [+207.52s] DEBUG: Process 1671 exited with return value 0 [+207.52s] DEBUG: XServer 0: X server stopped [+207.52s] DEBUG: Releasing VT 7 [+207.52s] DEBUG: XServer 0: Removing X server authority /var/run/lightdm/root/:0 [+207.52s] DEBUG: Seat seat0: Display server stopped [+207.52s] DEBUG: Seat seat0: Active display server stopped, starting greeter [+207.52s] DEBUG: Seat seat0: Creating greeter session [+207.52s] DEBUG: Seat seat0: Creating display server of type x [+207.52s] DEBUG: Using VT 7 [+207.52s] DEBUG: Seat seat0: Starting local X display on VT 7 [+207.52s] DEBUG: XServer 0: Logging to /var/log/lightdm/x-0.log [+207.52s] DEBUG: XServer 0: Writing X server authority to /var/run/lightdm/root/:0 [+207.52s] DEBUG: XServer 0: Launching X Server [+207.52s] DEBUG: Launching process 2868: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch [+207.52s] DEBUG: XServer 0: Waiting for ready signal from X server :0 [+208.44s] DEBUG: Got signal 10 from process 2868 [+208.44s] DEBUG: XServer 0: Got signal from X server :0 [+208.44s] DEBUG: XServer 0: Connecting to XServer :0 [+209.25s] CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed [+209.25s] DEBUG: Seat seat0: Display server ready, starting session authentication [+209.25s] DEBUG: Session pid=2872: Started with service 'lightdm-greeter', username 'lightdm' [+209.28s] DEBUG: Session pid=2872: Authentication complete with return value 0: Success [+209.28s] DEBUG: Seat seat0: Session authenticated, running command [+209.28s] DEBUG: Session pid=2872: Running command /usr/lib/lightdm/lightdm-greeter-session /usr/sbin/lightdm-gtk-greeter [+209.28s] DEBUG: Creating shared data directory /var/lib/lightdm-data/lightdm [+209.28s] DEBUG: Session pid=2872: Logging to /var/log/lightdm/seat0-greeter.log [+209.33s] DEBUG: Activating VT 7 [+209.33s] DEBUG: Activating login1 session c5 [+209.34s] DEBUG: Seat seat0 changes active session to c5 [+209.34s] DEBUG: Session c5 is already active [+209.42s] DEBUG: Greeter connected version=1.24.0 api=1 resettable=false [+209.63s] DEBUG: Greeter start authentication for lyon [+209.63s] DEBUG: Session pid=2928: Started with service 'lightdm', username 'lyon' [+209.65s] DEBUG: Session pid=2928: Got 1 message(s) from PAM [+209.65s] DEBUG: Prompt greeter with 1 message(s) [+212.04s] DEBUG: Seat seat0 changes active session to 4 [+216.92s] DEBUG: Seat seat0 changes active session to 8 I can start a session from VT1, using 'startx'.