Using separate users
During installation of Ubuntu, a single user and password is created. However, in order to keep your computer and documents safe, it is important to use a separate user account for each person that uses the computer. In this way, multiple users can have access to the computer while preserving and protecting their own personal settings and files.
To modify the users or groups on your system, you can use the Users And Groups application located in System → Administration → Users and Groups.
Managing groups of users
To add a new group, select the Groups tab and click Add group. Choose a name for the new group and, if you want, change the default value for the Group ID. If you try to allocate a Group ID that is in use, the system will warn you.
To remove a user or a group from the system, select the user or group you want to delete and click Delete.