used webmin for most of my user administration in the past just because of the ease of use, however Ive been trying to move away from webmin and do everything myself from the command line lately so Ive gotten back into adding users and managing passwords and groups from the command line.
Read it here
When I was first learning Linux, my instructor said that one thing that makes Linux different from Windows is that Linux assumes you know what youre doing from the start. Specifically when youre logged in as root, you get very cryptic messages if at all, for the sole reason that the command line assumes you know what youre doing and dont need any sort of notice or confirmation. Keep this in mind whenever you do anything from the command line.