Users and groups in Linux

Adding user

In linux, or at least Ubuntu, a user can be added using:

adduser username

adduser is a user-friendly command that uses useradd as back-end. Thus, adduser should be prefered to useradd.

Adding user to a group

A user can be added to a group using:

adduser username groupname

This can be used to allow users to use sudo:

adduser username sudo