gnome-shell error log

Question

Where can I find gnome-shell error (or debug) log?

I'm interested in mutter error/warning messages since I have a GLX problem I need to debug and I believe the key could be in gnome-shell's messages.

Solution

I'd start with journald's logs. Try one of these:

$ journalctl /usr/bin/gnome-shell
$ journalctl /usr/bin/gnome-session

If the logs are not there then try this:

$ journalctl -xe

Googling I did find this thread titled: gnome-session logging which did have several examples that worked when I tried them on an Ubuntu 16.04 system I have.

SYSLOG_IDENTIFIER=gnome-session-binary

$ journalctl SYSLOG_IDENTIFIER=gnome-session-binary -n 5
-- Logs begin at Sun 2018-07-15 06:33:41 EDT, end at Sat 2018-07-21 00:23:03 EDT. --
Jul 16 18:35:21 manny gnome-session-binary[17047]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Jul 16 18:35:21 manny gnome-session-binary[17047]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Jul 16 18:35:21 manny gnome-session-binary[17047]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Jul 17 02:11:43 manny gnome-session-binary[18526]: Entering running state
Jul 17 13:08:48 manny gnome-session-binary[23495]: Entering running state

SYSLOG_IDENTIFIER=gnome-session

$ journalctl SYSLOG_IDENTIFIER=gnome-session -n 5
-- Logs begin at Sun 2018-07-15 06:33:41 EDT, end at Sat 2018-07-21 00:23:03 EDT. --
Jul 20 06:30:10 manny gnome-session[18526]: (gnome-software:18773): Gs-WARNING **: failed to call gs_plugin_refresh on apt: apt transaction returned result exit-failed
Jul 20 06:30:10 manny gnome-session[18526]: (gnome-software:18773): Gs-WARNING **: failed to refresh the cache: no plugin could handle refresh
Jul 20 07:36:18 manny gnome-session[18526]: Nautilus-Share-Message: Called "net usershare info" but it failed: 'net usershare' returned error 255: mkdir failed on directory /var/run/samba/msg.l
Jul 20 07:36:18 manny gnome-session[18526]: net usershare: cannot open usershare directory /var/lib/samba/usershares. Error No such file or directory
Jul 20 07:36:18 manny gnome-session[18526]: Please ask your system administrator to enable user sharing.

.xsession-errors

$ tail -n 5 ~/.xsession-errors
upstart: indicator-session main process (25074) killed by TERM signal
upstart: indicator-application main process (25139) killed by TERM signal
upstart: unity7 main process (25334) terminated with status 1
upstart: unity-panel-service-lockscreen main process (32162) killed by HUP signal
upstart: Disconnected from notified D-Bus bus