Restore disk in single user mode
Normally you can't. If you boot into single-user mode you'll find that diskutil can't run because it's required modules aren't available.

You can try this: http://sabiancrash.blogspot.com/2011/06/how-to-run-diskutil-in-single-user-mode.html

But, the easiest way would be to use an OSX install CD. Boot from the CD (put it in, hold C at boot). When the installer first loads you can choose Disk Utility from the Tools menu.