How can I find out what password I need to use for 'su'?

I am using Mac OS X 10.5, and have my account set up so that I don't need to login. When I go to Network Preferences and click the lock icon on the lower left corner, I am prompted for my username and password. I simply enter my password and the lock icon becomes unlocked.

But when I go to a shell and enter su, I get this:

$ su
Password:
su: Sorry

What password do I enter here?

Solution 1:

For suing you would ned the password of the target account, root in this case. But on Mac OS X, root doesn't have a password, su this will never work. You can however use sudo -i which will give you a root shell too. You need to enter your user's password there.

Solution 2:

Enter sudo su. You can use your own password then.