I’m seeing an odd problem on Fedora 32. I issue the command
sudo usermod -G groupname -a username
for my own username. The command runs. I check the /etc/group file and I am still listed as a member of all the groups I used to be a member of plus the new group.
I then log out of the graphical desktop and log back in (specifically so I can get my new group membership). Upon opening a terminal shell and issuing the ‘groups’ command, I only see the old list of groups for my account. No matter how many times I do this, I won’t be a member of the newly added group. If I reboot the system, and log in afterwards, only then will I be a member of the new group.
So why isn’t a group membership change taking effect just upon logging in again?
5.9.15-100.fc32.x86_64 #1 SMP Wed Dec 16 16:49:20 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Note that this has been happening since at least kernel 5.8. Not sure how far back it has been happening, since my group membership doesn’t change that often.