6.3.2.3. /etc/group

The /etc/group file is world-readable and contains a list of groups, each on a separate line. Each line is a four field, colon delimited list including the following information:
  • Group name — The name of the group. Used by various utility programs as a human-readable identifier for the group.
  • Group password — If set, this allows users that are not part of the group to join the group by using the newgrp command and typing the password stored here. If a lower case x is in this field, then shadow group passwords are being used.
  • Group ID (GID) — The numerical equivalent of the group name. It is used by the operating system and applications when determining access privileges.
  • Member list — A comma delimited list of the users belonging to the group.
Here is an example line from /etc/group: 
 general:x:502:juan,shelley,bob
This line shows that the general group is using shadow passwords, has a GID of 502, and that juan, shelley, and bob are members.
For more information on /etc/group, see the group(5) man page.