Linux Add User To Group

useradd Example - Add A New User To Secondary Group

You need to the useradd command to add new users to existing group (or create a new group and then add user). If group does not exist, create it. The syntax is as follows:



useradd -G {group-name} username

In this example, create a new user called vivek and add it to group called developers. First login as a root user (make sure group developers exists), enter:


# grep developers /etc/group

Output:

developers:x:1124:

If you do not see any output then you need to add group developers using groupadd command:


# groupadd developers

Next, add a user called vivek to group developers:


# useradd -G developers vivek

Setup password for user vivek:


# passwd vivek

Ensure that user added properly to group developers:


# id vivekOutput:

uid=1122(vivek) gid=1125(vivek) groups=1125(vivek),1124(developers)

Please note that capital G (-G) option add user to a list of supplementary groups. Each group is separated from the next by a comma, with no intervening whitespace. For example, add user jerry to groups admins, ftp, www, and developers, enter:


# useradd -G admins,ftp,www,developers jerry



useradd example - Add a new user to primary group

To add a user tony to group developers use following command:


# useradd -g developers tony


# id tony

Sample outputs:

uid=1123(tony) gid=1124(developers) groups=1124(developers)

Please note that small -g option add user to initial login group (primary group). The group name must exist. A group number must refer to an already existing group.

usermod example - Add a existing user to existing group

Add existing user tony to ftp supplementary/secondary group with usermod command using -a option ~ i.e. add the user to the supplemental group(s). Use only with -G option :


# usermod -a -G ftp tony

Change existing user tony primary group to www:


# usermod -g www tony