- Read The Fine Manual
$ man usermod
- Become root
- Check if the group exists, and if it doesn't, create it
# groupadd mygroup groupadd: group 'mygroup' already exists
- Add user to the group
# usermod -a -G mygroup myuser
There are caveats, of course. For example, the above doesn't work when using LDAP/Kerberos login:
# usermod -a -G vboxusers borlbej usermod: Account `borblej' does not exist.
In openSUSE, we use Yast (Security and Users -> User and Group Management) for this. (Hint: "Set Filters".)
In the old days, we would typically just edit
The new group setting takes effect only after logging out and logging back in. If using a desktop environment, one must log out of the desktop, not just close the terminal window.