Tim:
Only if you explicitly switch over to run level three. X is usually running, automatically, in run level five. But you can start and stop X by hand, and remain in run level three. You can use the telinit command to switch levels, and it will start and stop X, as well, if the defaults are left to run it on level five, and not to run it on level three.
Oops! I neglected to mention that I use ctrl-alt-functionkey to switch (then c-a-F7 to switch back).
Your response makes it sound like there are other ways to accomplish what I want. Actually, I *really* want to _turn off X_. Is there yet another way to do this (other than c-a-fk and telinit)? Note that I leave all my computers run (crunching on distributed processing projects); I use 5 (GUI), and want to turn off X when I'm not using the computer.
Regarding telinit - do I have to be su to use it?