Users and Groups

Since Linux is a true multi-user system, the principles of both users and groups are important to the internal operation of the system, and also to the day-to-day use of the system. The way Linux handles users and groups makes it one of the most secure operating systems.

Users

There are two different types of users:

  • Physical Users are people who use the system physically. They have user IDs which are usually unique, as well as group IDs.

  • Logical Users are not tied to a person, but instead are tied to a system function that are used by applications to perform specific tasks. Daemons, mail, and news are examples of logical users.

Groups

Groups are logical expressions of organization. They tie users together and provide group-based, rather than user-based, permissions. Common groups include admin, audio, and mail.