Here's how you do it. Use pico or vi in the Terminal and edit /Library -> Preferences -> com.apple.loginwindow.plist as root. Make the following change where noted (italicized and extra-indented in the "after" section):
Before:
... <key>SHOWFULLNAME</key> <true/> <key>lastUser</key> <string>loggedIn</string> <key>lastUserName</key> ...After:
... <key>SHOWFULLNAME</key> <true/> <key>autoLoginUser</key> <string>>console</string> <key>lastUser</key> <string>Restart</string> <key>lastUserName</key> ...Notice the extra ">" in the line with "console" in it (this is to pass ">console" as the login user name). Now reboot, and you will never get the GUI at bootup. It's command line only from that point forward. If you want to go back, edit the file again, and remove those two lines, and reboot.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030603183119799