This tutorial will explain how to Add,Modify and Delete Users,Groups in Ubuntu.Linux users can login to the system and use with the provided previliges. Linux groups are a mechanism to manage a collection of computer system users. All Linux users have a user ID and a group ID and a unique numerical identification number called a userid (UID) and a groupid (GID) respectively. Groups can be assigned to logically tie users together for a common security, privilege and access purpose.