How to Add a User to Webmin Via Command Lineby Joshua Laud
If you're using Webmin to control your and administrate your Unix-based server, then you'll eventually need to know how to add new users. Webmin is primarily developed for administrating Web-based servers and has a number of Web applications pre-installed to its operation. If you're connected to Webmin via your Terminal, then you'll need to learn how to add users using the command line. This involves invoking typical Unix commands and then associating that user account with Webmin.
Type "useradd" in your Terminal window and press "Enter." Follow the onscreen prompts to add a new user to Linux.
Type "sudo pico /etc/shadow" and press "Enter." Enter your password and press "Enter." This opens the shadow command, where Webmin user details are stored.
Type "user:password:0::" replacing both "user" and "password" with the user name and password of your account that you created.
Press "Esc" and then "Y" to save changes.