Well switching from nVidia propietry drivers to the open source Nouveau drivers for nVidia GPU’s I found I had no 3D acceleration, and when running glxinfo etc I was getting
Error: couldn't find RGB GLX visual or fbconfig
And in Xorg.log.0 output file I was seeing
Failed to load module "glx" (loader failed, 7)
Turns out after stuffing around trying to find a solution, I did a search to find the package that held libglx.so and that was in the xserver-xorg-core. Well I reinstalled xserver-xorg-core and it fixed the problem and I now have 3D goodness
# apt-get install --reinstall xserver-xorg-core
Well I thought I’d have another play with Nouveau the open source driver for nVidia GPU’s, as it been a while since played around with them. Since the last time I played with Nouveau it was very buggy and unstable and 3D support was even worse, but I very surprised that there is some 3D support via Gallium3D.
Anyways this how I setup my xorg.conf for dual head setup with nouveau under Debian testing (wheezy):
Option "PreferredMode" "1920x1080_60.00"
Option "PreferredMode" "1440x900_60.00"
Option "RightOf" "monitor0"
VendorName "nVidia Corporation"
BoardName "GeForce GT 220"
Option "Monitor-DVI-I-1" "monitor0"
Option "Monitor-VGA-1" "monitor1"
Virtual 3360 1080
At the moment I am very happy with Nouveau and going to keep using it till it borks it again
Also if you not want to go through the hassle of xorg.conf you could run or put this in your session startup file, example this what I used for testing with ~/.fluxbox/startup
$ xrandr --output DVI-I-1 --mode 1920x1080 --pos 0x0 && xrandr --output VGA-1 --mode 1440x900 --pos 1920x0 &
The above does the same as the above xorg.conf configuration.