Adding group members

Users tom and jerry are both cartoon characters, so it makes sense to add them both to the cartoon group.

To add tom to the cartoon group, you simply run the command usermod -aG cartoon tom:

root@ubuntu-linux:~# usermod -aG cartoon tom

Likewise, you can add jerry to the cartoon group:

root@ubuntu-linux:~# usermod -aG cartoon jerry

Now, let's have a peek at the /etc/group file:

root@ubuntu-linux:~# tail -n 2 /etc/group 
cartoon:x:1009:tom,jerry 
developers:x:888:

As you can see, both tom and jerry are now listed as members of the cartoon group.

You can use the id command to view the group memberships of any user on the system. For example, if you want to check which groups tom belongs to, you can run the command id tom:

root@ubuntu-linux:~# id tom
uid=444(tom) gid=1007(tom) groups=1007(tom),1009(cartoon)

Let's do some more practice by creating three new users – sara, peter, and rachel:

root@ubuntu-linux:~# useradd -m sara 
root@ubuntu-linux:~# useradd...