Tools for building new Debian systems.
https://wiki.debian.org/NvidiaGraphicsDrivers#Debian_7_.22Wheezy.22
apt-get install lightdm
Sources.list :
deb http://http.debian.net/debian/ wheezy main contrib non-free
apt-get install linux-headers-$(uname -r|sed 's,[^-]*-[^-]*-,,') nvidia-kernel-dkms