I'm using Ubuntu 16.04. When I use LightDM to login and start X, I see that my secondary groups aren't loaded (running "groups" reports that I belong only to my primary group). If I log in via console or if I su in a term in X, the groups command works normally, reporting my primary and all of my secondary groups.
Curiously, even though "groups" does not report that I'm a member of sudoers, I can still sudo. Similarly, I can run mythfrontend, even though I'm not reportedly a member of mythtv. It seems as if the OS recognizes my secondary groups, even if the groups command does not.
So, it doesn't seem to cause a real problem, but I'm curious if anyone else has seen this behavior. I have three other machines running Ubuntu 16.04, but groups works normally on each of them.
Best Answer
I've got my exact problem fixed, thanks to the defect reported here https://bugzilla.redhat.com/show_bug.cgi?id=1581495
I had errors logged into the
/var/log/auth.log
which made me suspect problems around this.These Ubuntu package was updated yesterday,
libpam-kwallet4:amd64 (4:5.5.5-0ubuntu1.2, 4:5.5.5-0ubuntu1.3), libpam-kwallet5:amd64 (4:5.5.5-0ubuntu1.2, 4:5.5.5-0ubuntu1.3)
and this must have caused the trouble. I just commented out the following lines in/etc/pam.d/lightdm
and a reboot saved my day