How do I startup Xserve OS X without the GUI?
Solution 1:
OS X does not have runlevels. It natively boots into the GUI. If you want you can set the server to not auto-login and just list the username and password fields on boot. From there you can type ">console" in the user field and press return. This will exit the GUI and drop you into a shell.
May I ask what you want to accomplish by booting into "runlevel 3"?