I'm having the exact and/or similar problem, but I'm running on an Arch based distro. My Log is as follows:
[+0.09s] DEBUG: Logging to /var/log/lightdm/lightdm.log [+0.09s] DEBUG: Starting Light Display Manager 1.24.0, UID=0 PID=488 [+0.09s] DEBUG: Loading configuration dirs from /usr/share/lightdm/lightdm.conf.d [+0.09s] DEBUG: Loading configuration dirs from /usr/local/share/lightdm/lightdm.conf.d [+0.09s] DEBUG: Loading configuration dirs from /etc/xdg/lightdm/lightdm.conf.d [+0.09s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf [+0.09s] DEBUG: Registered seat module local [+0.09s] DEBUG: Registered seat module xremote [+0.09s] DEBUG: Registered seat module unity [+0.09s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager [+0.09s] DEBUG: Monitoring logind for seats [+0.09s] DEBUG: New seat added from logind: seat0 [+0.09s] DEBUG: Seat seat0: Loading properties from config section Seat:* [+0.09s] DEBUG: Seat seat0: Starting [+0.09s] DEBUG: Seat seat0: Creating greeter session [+0.15s] DEBUG: Seat seat0: Creating display server of type x [+0.15s] DEBUG: Could not run plymouth --ping: Failed to execute child process “plymouth” (No such file or directory) [+0.15s] DEBUG: Using VT 7 [+0.15s] DEBUG: Seat seat0: Starting local X display on VT 7 [+0.15s] DEBUG: XServer 0: Logging to /var/log/lightdm/x-0.log [+0.19s] DEBUG: XServer 0: Writing X server authority to /run/lightdm/root/:0 [+0.19s] DEBUG: XServer 0: Launching X Server [+0.19s] DEBUG: Launching process 497: /usr/bin/X :0 -seat seat0 -auth /run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch [+0.19s] DEBUG: XServer 0: Waiting for ready signal from X server :0 [+0.19s] DEBUG: Acquired bus name org.freedesktop.DisplayManager [+0.19s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0 [+3.10s] DEBUG: Loading users from org.freedesktop.Accounts [+3.10s] DEBUG: User /org/freedesktop/Accounts/User1000 added [+7.73s] DEBUG: Got signal 10 from process 497 [+7.73s] DEBUG: XServer 0: Got signal from X server :0 [+7.73s] DEBUG: XServer 0: Connecting to XServer :0 [+7.73s] CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed [+7.73s] DEBUG: Seat seat0: Display server ready, starting session authentication [+7.73s] DEBUG: Session pid=524: Started with service 'lightdm-greeter', username 'lightdm' [+7.94s] DEBUG: Session pid=524: Authentication complete with return value 0: Success [+7.94s] DEBUG: Seat seat0: Session authenticated, running command [+7.95s] DEBUG: Launching process 527: /usr/bin/numlockx on [+8.03s] DEBUG: Process 527 exited with return value 0 [+8.03s] DEBUG: Seat seat0: Exit status of /usr/bin/numlockx on: 0 [+8.03s] DEBUG: Session pid=524: Running command /usr/bin/lightdm-gtk-greeter [+8.03s] DEBUG: Creating shared data directory /var/lib/lightdm-data/lightdm [+8.03s] DEBUG: Session pid=524: Logging to /var/log/lightdm/seat0-greeter.log [+8.47s] DEBUG: Activating VT 7 [+8.47s] DEBUG: Activating login1 session c1 [+8.47s] DEBUG: Seat seat0 changes active session to c1 [+8.47s] DEBUG: Session c1 is already active [+10.95s] DEBUG: Greeter connected version=1.24.0 api=1 resettable=false [+12.80s] DEBUG: Greeter start authentication for kool [+12.80s] DEBUG: Session pid=598: Started with service 'lightdm', username 'kool' [+13.03s] DEBUG: Session pid=598: Got 1 message(s) from PAM [+13.03s] DEBUG: Prompt greeter with 1 message(s) [+22.27s] DEBUG: Continue authentication [+22.30s] DEBUG: Session pid=598: Authentication complete with return value 0: Success [+22.30s] DEBUG: Authenticate result for user kool: Success [+22.30s] DEBUG: User kool authorized [+22.36s] DEBUG: Greeter requests session xfce [+22.37s] DEBUG: Seat seat0: Stopping greeter; display server will be re-used for user session [+22.37s] DEBUG: Terminating login1 session c1 [+22.37s] DEBUG: Session pid=524: Sending SIGTERM [+22.66s] DEBUG: Greeter closed communication channel [+22.66s] DEBUG: Session pid=524: Exited with return value 0 [+22.66s] DEBUG: Seat seat0: Session stopped [+22.66s] DEBUG: Seat seat0: Greeter stopped, running session [+22.66s] DEBUG: Registering session with bus path /org/freedesktop/DisplayManager/Session0 [+22.66s] CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed [+22.66s] DEBUG: Session pid=598: Running command /etc/lightdm/Xsession startxfce4 [+22.67s] DEBUG: Creating shared data directory /var/lib/lightdm-data/kool [+22.67s] DEBUG: Session pid=598: Logging to .xsession-errors [+23.26s] DEBUG: Activating VT 7 [+23.26s] DEBUG: Activating login1 session c2 [+23.26s] DEBUG: Seat seat0 changes active session to [+23.26s] DEBUG: Seat seat0 changes active session to c2 [+23.26s] DEBUG: Session c2 is already active -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to lightdm in Ubuntu. https://bugs.launchpad.net/bugs/1699637 Title: g_object_unref: assertion 'G_IS_OBJECT (object)' failed Status in Light Display Manager: New Status in lightdm package in Ubuntu: Confirmed Bug description: lightdm work fine with xfce4(arch linux),but when i check it's status by systemd,it show this message. Jun 21 15:55:38 archlinux systemd[1]: Starting Light Display Manager... Jun 21 15:55:38 archlinux systemd[1]: Started Light Display Manager. Jun 21 15:55:38 archlinux lightdm[417]: g_object_unref: assertion 'G_IS_OBJECT (object)' failed Jun 21 15:55:38 archlinux lightdm[465]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid Jun 21 15:55:47 archlinux lightdm[417]: g_object_unref: assertion 'G_IS_OBJECT (object)' failed Jun 21 15:55:47 archlinux lightdm[607]: pam_unix(lightdm:session): session opened for user jaken by (uid=0) Jun 21 17:58:33 archlinux lightdm[417]: g_object_unref: assertion 'G_IS_OBJECT (object)' failed To manage notifications about this bug go to: https://bugs.launchpad.net/lightdm/+bug/1699637/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp