Add 3 users: harry, natasha, tom.
The requirements: The Additional group of the two users: harry, Natasha is the admin group. The user: tom’s login shell should be non-interactive.

# useradd -G admin harry
# useradd -G admin natasha
# useradd -s /sbin/nologin tom
# id harry;id Natasha (Show additional group)
# cat /etc/passwd
(Show the login shell)

OR

# system-config-users