How to add an additional Super User in Ubuntu
You can give Super User status to any additional user in Ubuntu by giving SUDO access.
When you set up Ubuntu, it automatically adds the first user to the sudo group. As it doesn't automatically add additional users to the sudo group and if you want to give someone else superuser privileges on your shared system, you'll have to give them sudo access.
To add new users to sudo, you need to use the usermod command. Run sudo usermod -G admin username . However, if the user is already a member of other groups, you'll want to add the -a option, like so: sudo usermod -a -G admin username .
The other way to do this will be by going to System > Administration > Users and Groups.
Select the user you want to add to sudo, and click Properties.