Got same issue after an upgrade from Ubuntu 14.04 to 16.04 and the following actions solved the problem :
sudo pam-auth-update --force sudo vi/etc/pam.d/lightdm => add following lines at the end : session required pam_loginuid.so session required pam_systemd.so sudo reboot -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1240336 Title: After release upgrade, the user looses permissions for several basic actions in the system To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm/+bug/1240336/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs