An earlier hint showed us how to use such command line tools as diskutil and installer while in single user mode under Mac OS X 10.3. I wanted to do the same thing, but while starting up from the Mac OS X Install CD. Since the CD itself is write protected, there are couple of additional steps needed to make this work. The good thing is that all the steps are actually right there in a file called rc.cdrom, located in /etc. The only thing we have to make sure is that the script rc.cdrom ends before it invokes the GUI and starts the Installer application.
We still have the problem that the CD is write-protected, so we cannot just edit the rc.cdrom file and run it. Apart from that, there is no text editing tool (like vi or pico) installed on the CD. But luckily there is a tool named head. With head, you can print a self-defined count of lines back to the shell from the file you specify.
The most important thing is to find the line you would want the rc.cdrom script to stop at. I guess that would be right before the /System/Installation/CDIS/splash command is defined. In my case, that was line 168. Adapt the line number to the rc.cdrom script you find on your Install CD in /etc/. So finally here's the walkthru:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20041108063942847