Creating and managing groups on Linux

On Linux®, providing you are not using NIS or NIS+, use the /etc/group file to work with groups.

About this task

On Linux, group information is held in the /etc/group file. You can use commands to create a group, add a user to a group, display a list of the users who are in the group, and remove a user from a group.

Procedure

To create a new group, use the groupadd command.
Type the following command:
```
groupadd -g group-ID group-name
```
where group-ID is the numeric identifier of the group, and group-name is the name of the group.
To add a member to a supplementary group, use the usermod command to list the supplementary groups that the user is currently a member of, and the supplementary groups that the user is to become a member of.
For example, if the user is already a member of the group groupa, and is to become a member of groupb, use the following command:
```
usermod -G groupa,groupb user-name
```
where user-name is the user name.
To display who is a member of a group, use the getent command.
Type the following command:
```
getent group group-name
```
where group-name is the name of the group.
To remove a member from a supplementary group, use the usermod command to list the supplementary groups that you want the user to remain a member of.
For example, if the user's primary group is users and the user is also a member of the groups mqm, groupa and groupb, to remove the user from the mqm group, use the following command:
```
usermod -G groupa,groupb user-name
```
where user-name is the user name.