That might be more useful in a general (disk) booting scenario. From the liveCD, just add the runlevel to the end and hit <Enter> (I think).
Personally (when I do something like this) I normally boot to single user mode (runlevel 1).
Of course, runlevels are somewhat meaningless with systemd.
Last edited by syg00; 10-06-2012 at 08:56 PM.