The /etc/group file contains a list of groups on the system. The records in the /etc/group file will contain 4 fields. The 4 fields are: group name:password:GID:group members.

[root@server1 ~]# cat /etc/group
group1:x:1001:

Change group name

The -n or --new-name option can be used to change the name of a group. For example, to change the group name from group1 to group2:

[root@server1 ~]# groupmod -n group2 group1

The /etc/group file will now have group2 as the group name.

[root@server1 ~]# cat /etc/group
group2:x:1001:

Add or change group password

The -p or --password option can be used to add or change the password for the group. Adding or changing a group password using the groupadd or groupmod commands will create an unencrypted, cleartext password. Adding or changing a group password using the gpasswd command will create an encrypted password.

[root@server1 ~]# groupmod -p Password123 group1

Similarly, the gpasswd groupname command can be used to secure a group with an encrypted password.

Regardless if the group is or is not secured with a password, the second field of /etc/group will display an "x", so viewing the /etc/group file does not help to know if the group is secured with a password.

[root@server1 ~]# cat /etc/group
group1:x:1001:

The /etc/gshadow file will contain the group password.

[root@server1 ~]# cat /etc/gshadow
group1:Password123::

Change GID

The -g or --gid option can be used to change the GID of a group. For example, to change the GID of group1 from 1001 to 1234.

[root@server1 ~]# groupmod -g 1234 group1

Group1 will now have GID 1234.

[root@server1 ~]# cat /etc/group
group1:x:1001:

By default, the system expects each group to have a unique GID. When attempting to change the GID to a GID already in use, an error will appear.

[root@server1 ~]# groupadd -g 1234 group2
groupmod: GID '1234' already exists

The -o or --non-unique option can be used to create a new group using a GID already being used by another group.

[root@server1 ~]# groupadd -og 1234 group2

In this example, there will now be two groups with GID 1234.

[root@server1 ~]# cat /etc/group
group1:x:1234:
group2:x:1234:

Add group members

There is no option to add members to a group with the groupmod command. The usermod command can be used to add members to a group.