So you want to boot into a non graphical, multi-user Mac OS X command line interface, eh?
The single-user command line is where we'll start, but first we need to create a script to make our single-user darwin into the multi-user darwin system that we are after. So we'll make a copy of /private/etc/rc, and rename it to something like /private/etc/rc.mu. Next, open this new file in your favorite text editor and scroll all the way to the second to last line that says:
SystemStarter -g ${VerboseFlag} ${SafeBoot} This is the only line we will edit. We want a text boot, so we will remove the -g (graphical boot) flag, to make the line look like this: SystemStarter ${VerboseFlag} ${SafeBoot}
Now its time to reboot your system while holding Command-S to boot to a single user, root system. Once you get to the prompt, type sh /private/etc/rc.mu and watch all the pretty startup text fly by. This brings up everything a normal Mac OS X startup would, except for bringing up Aqua.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030714044058502