If you are not logged in as the root user, type the command Su-and then enter the root password to switch to root user mode.
1. Create a new User: At the command line, type Useradd, followed by a space and the user name of the new user you created (for example, Useradd GUACM), press the [Enter] key.
2. Set a password for the new user: type passwd, followed by a space and the user name (for example, passwd GUACM), press the [Enter] key.
Under new password: prompt, enter a password for the new user, and then press [Enter].
At Retype new password: prompt, enter the same password to confirm your selection, and then press [Enter].
If the settings are correct, you will be prompted: All authentication tokens update successfully.
This article is from "Dream Dreams" blog, please be sure to keep this source http://dreamy.blog.51cto.com/12471447/1911021
Linux to create a new user account at the shell prompt