group
System group database file
TLDR
View group file
$ cat /etc/group
Find groups for user$ groups [username]
Find group by name$ getent group [groupname]
List group members$ getent group [groupname] | cut -d: -f4
DESCRIPTION
/etc/group is the system file that defines groups and their members. Each line contains a group entry with four colon-separated fields: group name, password placeholder, numeric GID, and a comma-separated list of member usernames.
Groups control file access permissions and are fundamental to Unix security. Users can belong to multiple groups, with one primary group set in /etc/passwd.
FILE FORMAT
$ groupname:password:GID:members
Fields:- groupname: Group name
- password: Usually 'x' (see /etc/gshadow)
- GID: Numeric group ID
- members: Comma-separated list of users
RELATED COMMANDS
$ groupadd groupname # Create group
groupdel groupname # Delete group
groupmod -n new old # Rename group
gpasswd -a user group # Add user to group
gpasswd -d user group # Remove user from group
newgrp groupname # Switch primary group
groupdel groupname # Delete group
groupmod -n new old # Rename group
gpasswd -a user group # Add user to group
gpasswd -d user group # Remove user from group
newgrp groupname # Switch primary group
CAVEATS
Direct editing not recommended; use groupadd/groupmod. Changes may require logout to take effect. GIDs below 1000 typically reserved for system groups.
