Robb Tracy Explains Linux User Accounts and Passwords
This lesson is designed to teach you where Linux user accounts are stored, how to manage user accounts from the command line, and how to manage user passwords from the command line. The role of the /etc/passwd and /etc/shadow files are discussed. The useradd, usermod,and userdel utilities are also addressed as well as the passwd utility.
The entire lesson is about 35 min. long, so I couldn't fit it all here. If you go to http://techmeds4wireheads.nebo-tech.com, you can view an interactive version (non-video) of the presentation in its entirety as well as a recorded demonstration of how to complete these tasks on a Linux system.