Users and Groups

Directly editing /etc/group is not recommended. groupadd & usermod modify /etc/gshadow as well

Add a Group to the System

groupadd [-r] -g <groupnumber> <groupname>

Add a User to a Group

usermod -a -G <groupname> <username>

Attic

usermod - Modify a user account (aus CVS-RCS-Howto)
chfn - change user name and information
adduser - Interactive front end to /usr/sbin/useradd for SW (Shellscript)
userdel - na was wohl? (aus SW-Book)
groupdel (aus SW-Book)