Install a Target-mode Mac without shutting down the host

Have you ever had a Mac that you need to reinstall, but only have a disk image of the install disc? Or, you don't have a DVD that the soon-to-be-reinstalled machine will accept?

So long as you have a Firewire cable, you can still run the install.

1. Put the target machine into Target mode (hold the "T" key as soon as you hear the chime on boot)
2. Connect the target machine and the host machine via FireWire cable
3. Insert the install DVD or mount the disk image on the host machine.
4. Open Terminal and enter this line:

   open /Volumes/Mac\ OS\ X\ Install\ DVD/System/Installation/Packages/

5. This will open a new Finder window displaying the contents of a folder on the install disc.

6. In that folder, you'll need to run OSinstall.mpkg and select the hard drive of the target machine as the install point. (you may want to format the hard drive of the target machine prior to doing the install)
7. Select your options (by clicking the "Customize" button) and you're off!

Note: this was written for 10.6.x. In some cases this works flawlessly, in others, it doesn't work at all. Please comment with your experience.