Which file defines the groups to which users belong in Linux systems?

The file that defines the groups to which users belong in Linux systems is /etc/group. This critical file stores information about the system's user groups, including the group name, password (if any), group ID (GID), and the list of users associated with each group.

Each line in the /etc/group file corresponds to a different group and follows a standard format, which is:

group_name:password:GID:user_list

• group_name: The name of the group.
• password: An optional field that was used for group passwords, though it is rarely used now.
• GID: The unique identifier for the group.
• user_list: A comma-separated list of usernames belonging to the group.

This file is essential for managing group permissions and access control on a Linux system. By defining groups in /etc/group, the system can efficiently determine access rights for different users based on their group memberships, which is fundamental for maintaining security and organization within the system.

The other options do not refer to the correct file or do not exist in standard Linux systems. For example, /etc/grouplist and /etc/usergroup are not standard files in Linux, while /usr/group