You can't "hide" users. I don't understand what you mean by "root doesn't show up in the list", because if you (for example) do either one of these:
Code:
cat /etc/group | grep root
cat /etc/passwd | grep root
you will get a line that reveals you that user
root exists. If you mean some graphical user interface tool doesn't "list" you root user, then it's a property of that tool; maybe there is no point in showing root user in the list. But surely you can't "hide" a user, and why would you want to?
Try these ones too, and if you don't want to get dull output, log in from different terminals as different users and then run the commands as some of the users and see what you get:
they should work unless you've configured your system otherwise. No way nor point in "hiding" user accounts.