Source:http://wiki.debian.org/Xorg
If xorg.conf is missing for some reason, Xorg will probe your hardware on every startup. Though this works fine in most cases, some settings remain inaccessible. To create a starting point for customization, do the following:
Switch to a console as root (not a terminal emulator in X), then run:
/etc/init.d/kdm stop
/etc/init.d/gdm stop
/etc/init.d/xdm stop
cd /etc/X11/
Xorg -configure
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Alternatively, reboot the machine in single user mode, then run:
cd /etc/X11/
Xorg -configure
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Follow the on-screen instructions. This should give you something to work with.
Run X
After installation run: startx
or as root run:
invoke-rc.d gdm