[clug] xorg config

David Tulloh david at tulloh.id.au
Fri Aug 28 21:46:27 MDT 2009

Mike Carden wrote:
> I have Ubuntu 8.04 Hardy (2.6.24 kernel) running on a desktop machine
> with an 'Intel Corporation 82945G/GZ' integrated video card. I have
> video, but OpenGL doesn't work. glxgears tells me:
> Xlib:  extension "GLX" missing on display ":0.0".
> Error: couldn't get an RGB, Double-buffered visual
> I looked inside xorg.conf and the penny dropped. It's a sawn-off
> xorg.conf these days with very little said about video cards, drivers
> or screens. All of that stuff is meant to be automatically set up
> (somewhere) at boot and you don't touch it. Using the old
> 'dkpg-reconfigure xserver-xorg'  only asks questions about the
> keyboard and mouse now, nothing about video.
> So is there another utility I ought to use to set this up or a
> resource that will help me manually craft a xorg.conf file to convince
> the graphics card to support OpenGL? My Google-Fu has failed me on
> this one
Hi Mike,

I've been playing around with these this week too.

If you specify a screen, device, monitor etc. it will use them as 
before.  If you don't specify then it will do it's funky magic trick.

I'm not sure about programs to do the configure for you, I've never 
trusted them and just done it myself.  The man page gives you a 
reference and you should be able to find examples online, essentially 
you need a severlayout, screen, monitor and device section.  I've never 
tried to have portions autodetected and portions specified manually but 
it probably works with the right incantations.

To load GLX you need the following snippet
Section "Module"
Load "glx"

If it still doesn't work at least the xorg log file should tell you 
why.  Checking that the driver is intel rather than vesa would be a good 

I was also playing with an Intel chip this week, I found when I upgraded 
to X 7.4 (Debian unstable) the autodetection worked.  However you also 
need to upgrade the kernel (they don't tell you that) as I believe it's 
making use of the new Gems graphics layer, I upgraded to Debian 2.6.30, 
if you don't do this it eats your processor whole.


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