What file contains user group memberships in Linux?

The file that contains user group memberships in Linux is /etc/group. This file is specifically designed to store details about the groups available on the system and associates each group with its members. Each line in this file represents a single group and includes the group name, password placeholder (if applicable), group ID (GID), and a comma-separated list of usernames that are members of that group.

In contrast, /etc/passwd contains information about user accounts, such as the username, user ID (UID), and home directory, but does not directly list group memberships. The /etc/sudoers file is used to define user privileges and restrictions regarding the use of the sudo command, while /etc/shadow stores user password information and account expiration details, which are also unrelated to user group memberships. Therefore, understanding that /etc/group is the designated file for managing and displaying user group memberships is fundamental to Linux system administration.