Call me dumb, but just installed Debian on a spare machine, have a problem with the mouse (not moving in gnome or KDE), but how do I log out of X/Gnome/KDE in order to log in as root to change the settings in XF86Config?

I can't log into a GUI as root, so how to I get back to the command line?

Rebooting the machine brings me straight into the Gnome GUI Manager where it asks me to log into a GUI.

Any help would be much appreciated!

CTRL-ALT-F1 through CTRL-ALT-F6 should take you to a console window, and should toggle you from one to another console window if you have more than one open.

ALT-F7 will restore your windows manager session.

"I can't log into a GUI as root, so how to I get back to the command line?"

Use:
<Ctrl> <Alt> <F3>
to get to a command line.

CTRL + ALT +F3 - Excellent, thankyou very much.

CTRL + ALT + Backspace just goes back to the gdm login screen.

Do you know of a way in which I can disable gdm from automatically running at startup? I want it to be optional, not always there at the start.

Or, is there such a thing as an F8 command? I've set up my gfx card wrong, and X crashes as soon as it loads.

Your humble Student,

"Do you know of a way in which I can disable gdm from automatically running at startup?"

Edit /etc/inittab

In the comments you will find a description of the 6 possible runlevels. One of the runlevels will be called "Full multiuser with network and xdm" (on SuSE this is runlevel 5, Debian gives it some other number). xdm is the program that calls gdm. You want to have xdm not automatically run at startup.

Another runlevel will be called "Full multiuser with network" (on SuSE this is runlevel 3, Debian gives it some other number)

You want to change the initdefault. Here is an example of changing SuSE from runlevel 5 to runlevel 3.

# The default runlevel is defined here
id:5:initdefault:

is changed to:

# The default runlevel is defined here
id:3:initdefault: