User Groups
I've logged out of the system as superman and logged back into michael (who still has sudo privileges.) Let's look at the groups that michael has been added to: groups
Some interesting entries, but the one we're interested in is sudo. We saw that in the sudoers file as %sudo. The group has all permissions, just like we gave to superman directly. So let's learn how-to modify an existing user and change the groups they have assigned to them.
Here's the groups superman has: sudo groups superman
Let's update those groups, placing superman in the sudo group: sudo usermod -a -G sudo superman
michael@develop:~$ sudo usermod -a -G sudo superman
michael@develop:~$ sudo groups superman
superman : superman sudo
Now let's log back into the superman user and see if we can re-create the spiderman user we deleted earlier:
superman@develop:~$ sudo adduser spiderman -gecos "Spiderman,,,,"
[sudo] password for superman:
Adding user `spiderman' ...
Adding new group `spiderman' (1002) ...
Adding new user `spiderman' (1002) with group `spiderman' ...
The home directory `/home/spiderman' already exists. Not copying from `/etc/skel'.
New password:
Retype new password:
passwd: password updated successfully
And it looks like I can use sudo visudo too:
Note
The message visudo: /etc/sudoers.tmp unchanged means I simply did Ctrl+X and exited visudo without making changes.
So the usermod command is used, as the name somewhat implies, to modify a user on the system. In the case above, we've modified a user's groups.