See also user (computing), Password management, Password fatigue, Authentication, Personal identification number (PIN), Password, Password manager, Single signon, MFA-2FA, Microsoft Hello, Apple Face ID, Facial recognition, Biometric authentication, Iris recognition, Retinal scan, Eye vein verification, Recognition, Fingerprint recognition
Unix-like operating systems identify a user by a value called a user identifier, often abbreviated to user ID or UID. The UID, along with the group identifier (GID) and other access control criteria, is used to determine which system resources a user can access. The Passwd (file) | password file maps textual User (computing) | user names to UIDs. UIDs are stored in the inodes of the Unix file system, running Process (computing) | processes, tar (computing) | tar archives, and the now-obsolete Network Information Service. In POSIX-compliant environments, the command-line UNIX commands | command Id (Unix) | id gives the current user's UID, as well as more information such as the user name, primary user group and group identifier (GID).
In Unix-like operating systems, a user identifier (often abbreviated to user ID or UID) is a value used to identify a user. The UID, along with the group identifier (GID) and other access control criteria, is used to determine which system resources a user can access. The password file maps textual user names to UIDs. UIDs are stored in the inodes of the Unix file system, running processes, tar archives, and the now-obsolete Network Information Service. In POSIX-compliant environments, the shell command
idgives the current user's UID, as well as more information such as the user name and the primary and supplementary group identifiers (GIDs) and group names.