Users and Groups

Each Linux user has a unique positive integer called user ID (uid) in addition to the username. The root user has the uid of 0.

Each process is associated with one uid (the user who starts running the program.) All the child processes inherit the uids of their parent processes.

Usernames and their uids are stored in the file /etc/passwd. You can find your user information (e.g., username, uid, home folder, default shell [e.g., bash, sh, or ksh]) by typing the following Linux command:

$ getent passwd "$( id -u )"

Each user belongs to a login group with a unique group ID (gid). This will be the user's primary group.

The user may also belong to a few supplemental groups, listed in /etc/group.

We will speak more about Users and Groups in Topic 7.