On Mon, 3 Feb 1997, Erik Bertelsen wrote:

> And if you are running xdm, the way to do it is to find xdm's pid and then
> kill xdm. Xdm will then close down and in the process of doing that, it
> will also stop the X server.

If you're running xdm, you probably don't have a getty running on the
console.  So unless you've got some other way to get into the system,
killing xdm probably won't help.  (I learned this the hard way, while
getting xdm running!)