To add new user in Linux you should have permission to do so. If you are the root user, you can add users into your Linux system.

The command adduser: 

In this example I’ve added user1 into Linux system. To check that user exists in the system, type: id username.

To change password for user, use the command passwd.

To remove user type user type: userdel

In this example user1 was removed, where the –r option means to remove the home folders and files created by/for user.