How does one refresh the groups that a logged-in user is in without having to re-login?
possible in shell (I don't think it is for gui)
I wrote more info on this on my blog a while back. according to that this will also change the default group of the shell. you can use
sg to Switch your default Group
su - username will do it for the shell (and subproccesses) that su opens up, but for everything else you'll need to relog.