Users and groups
Adding an existing user to an existing group
usermod -a -G theExampleGroup theExampleUserChanging the primary group of an existing user
usermod -g theExampleGroup theExampleUserSee wich groups the user belongs to
groups theExampleUserAdd an existing user to the sudo group
usermod -aG sudo usernameAdd a new user with name, shell and home directory
sudo useradd -m -c "Samwise the Brave" sam -s /bin/bash
https://www.cyberciti.biz/faq/howto-linux-add-user-to-group/
https://www.digitalocean.com/community/tutorials/how-to-create-a-sudo-user-on-ubuntu-quickstart