Is the SU password the same as admin password?

On the client version of Mac OS X, the root/su password is set to an illegal value by default, which means nobody can log in as root until it is changed from the Directory Utility(10.5), NetInfo Manager(10.4 and earlier), Workgroup Manager, or Terminal. On Mac OS X Server, the root password is the same as the original account's user password by default.

(29818)

You need to enable the root user first - see the following article:
http://docs.info.apple.com/article.html?artnum=106290

Cheers,
Bernd

su requires the password of the user you are switching to (typically root).

Why don't you just use plain sudo?

I reviewed the referenced link. I invoked Netinfo Manager.app. I unlocked the lock, and there was no "Security" tab/button to click, but under Users I clicked root. On root's properties the password showed just an asterisk ('*'); (I don't think I ever defined one when I first set this machine up), but I changed/set it. When locking the lock, "are you sure you want to make this change?" Yes. Window closed. Tried the utility again, to see if the new password took: in the "local @ localhost - /" window, the earlier (undefined, just Enter to blank password) unlocked the lock; the new password didn't.

In a Terminal window, when I supply the new password to a su root attempt, I still get "su: Sorry"

It's my personal machine, I'm the only one with admin privileges on it, and I'm trying to gain root so I can back up all users' (only me and 1 other) directories/files without being defeated due to permissions. No, "sudo <various rsback commands>" don't overcome the permissions issue.

How can I gain root in a Terminal session?