The groupadd command without any options can be used to create a new group. For example, to create a group named group1.

[root@server1 ~]# groupadd group1

The records in the /etc/group file will contain 4 fields. The 4 fields are: group name:password:GID:group members.

The /etc/group file contains group1. The group will not be secured with a password, in this example the GID is 1001, and the group does not have any members.

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

Password

The -p or --password option can be used to secure a group with a password. 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 ~]# groupadd -p Password123 group1

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::

GID

The -g or --gid option lets you choose the GID when creating a group.

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

In this example, the GID of group1 is 1234.

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

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

[root@server1 ~]# groupadd -g 1234 group2
groupadd: 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:

System group

The -r or --system option can be used to create a system group.

[root@server1 ~]# groupadd -r sysgroup

In this example, thereis a system group named sysgroup.

[root@server1 ~]# cat /etc/group
sysgroup:x:999:

Add group members

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