Removing User from Secondary Group in Linux ?

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

Example:

The following command will will remove user jack from mygrp group.

# gpasswd -d jack mygrp

Adding User to Secondary Group:

The following command will will add user jack to a secondary group named mygrp.

# usermod -aG mygrp jack