Adding User in Secondary Group using Command in Linux ?

Change <user_name> with your actual system user name and <group_name> with named of group to which you want to add user.

Example:

The following command will will add user jack to mygrp group.

# usermod -aG mygrp jack

Remove User from Secondary Group

The following command will remove user from secondary group. Please replace <user_name> and <group_name> with appropriate values.

$ sudo gpasswd  -d <user_name> <group_name>