•  Their is an application called users and groups in ubuntu which have a really simple and easy to use interface.With this application you could  add/delete/manage groups with relative ease.

• Goto system > administration > Users and Groups from your Ubuntu. 

Add/delete/manage users using Command line in Ubuntu

• To add user simply Go to applications-->accessories-->terminal and type the follwing

                                    sudo useradd -d /home/<username> -m <username>

                                    The -d is for creating the Home directory for the user

•      To Set the password for the new account use this;

                                    sudo passwd <username>

• Or if you want to have ubuntu run you through a wizard like process that asks for every piece of information use this:

                                    sudo adduser <username>

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