Description of problem:

Logging out and back in does not re-load the user's groups.

Version-Release number of selected component (if applicable):

gdm-3.22.3-1.fc25.x86_64

How reproducible: I tried several times, including with either X session or Wayland, all attempts had this problem.


Steps to Reproduce:
1. addgroup testgroup
2. usermod -a -G testgroup $USER
3. id -a $USER
4. log out of GNOME session
5. log in to GNOME again (using gdm)
6. id -a

Actual results:

uid=1000(alan-sysop) gid=1000(alan-sysop) groups=1000(alan-sysop),10(wheel),1003(testgroup)

uid=1000(alan-sysop) gid=1000(alan-sysop) groups=1000(alan-sysop),10(wheel) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

Expected results:

The groups in the output of `id -a $USER` and `id -a` should be the same, after logging out and back in again.

Additional info:

This is not 100% documented... the Fedora System Adminstrator's Guide doesn't mention *any* method to re-load groups, implying that they take effect immediately.  However the behaviour is widely expected, e.g. https://unix.stackexchange.com/a/11573/29483