Which file contains the list of all groups on a system?

The file that contains the list of all groups on a Linux system is located at /etc/group. This file serves as a central database for group information, storing the group name, password (if used), group ID (GID), and the members of the group.

Each entry in this file is structured in a way that enables the system to efficiently access group-related information. This is crucial for managing user permissions and access controls within the system. For instance, when a user logs in, the system checks their group memberships as defined in /etc/group to determine their access rights.

In contrast, /etc/passwd contains user account information, including usernames and user IDs, but does not specifically list groups. The other choices, such as /etc/groups and /group.txt, do not represent standard files in Linux for group information. While /etc/group is the correct and standard file for this purpose, the other names do not have any significance in the context of group management within Linux systems.