Once you have groups in place, you can add existing users as well as new users to that group. All access rights and permissions assigned to the group will be automatically available to all the members of the group.
You will need super user or root privileges to add a group member to the Ubuntu server. Follow these steps to add group members:
Step 1 : Here, you can use adduser command with two non-option arguments:
# sudo adduser <username> <group> sudo adduser tutorial groupdev
Step 2 : Enter your password to complete addgroup with root privileges.
Step 3 : Alternatively, you can use the command usermod to modify the group assigned to the user
sudo usermod -g <group> <username>
Step 4 : To add a user to multiple groups, use the following command:
sudo usermod -a -G <group1>,<group2>,<group3> <username>