Hey all,

How can I add users to groups, while keeping thier exising group memberships? I would prefer to be able to do this without a X utility also...
I have tried #usermod -g <username> and find that it changes membership, but I want to add membership, so that the user is a member of multiple groups.

You can edit /etc/group and just add the users name after other users in the particular groups you want them added to. For instance if you look at /etc/group on your box you will have entries like this:

root:x:0:root
bin:x:1:root,bin,daemon
daemon:x:2:root,bin,daemon
sys:x:3:root,bin,adm
adm:x:4:root,adm,daemon
tty:x:5:
disk:x:6:root

Say you also had a group called "chem" and it looked like this:

chem:x:30:you

and you wanted to add "me" to the group, just add me to the end of the line.

chem:x:30:you,me

That's all there is to it. To verify that the user was added successfully and that the system know this type "groups {username}".

Cool - thanks! I had seen the #groups <name> command, but forgot it.

What if instead of adding the username to /etc/group, you add the group next to the user in /etc/passwd? will it accomplish the same thing, or nothing at all?

It wouldn't have any meaning in /etc/passwd. It would probably just corrupt that entry, maybe the entire file.