Kill X in MDK8.2
 

how do I do that?

ctrl + alt + backspace

or login into another terminal and kill the process...

I try Ctrl + Del + Bksp, it only restarts X. I need to actually stop X from running.

Log in as root, and type init 3. To prevent X from starting automatically on restart, as root, edit the file /etc/inittab changing the line "id:5:initdefault:" to "id:3:initdefault:".

Basically you are telling Linux to switch runlevels (5 is X and 3 is console, aka "text mode"). The "id" line in /etc/inittab tells Linux what runlevel to run at startup by default.