[CentOS] /etc/X11/xorg.conf question

Mon Feb 2 17:35:57 UTC 2009
Paul Johnson <pauljohn32 at gmail.com>

On Fri, Jan 30, 2009 at 8:23 AM, Lanny Marcus <lmmailinglists at gmail.com> wrote:
> If I use "system-config-display" or "system-config-display --reconfig"
> although I get a message that I need to log out of GNOME, to have the
> new file written, for new Display Resolution, logging out or
> restarting the box does not result in the new settings for the Display
> taking hold. Sometimes, the number of colors is updated, but *never*
> the Resolution. Below is my xorg.conf file.  What do I need to include
> in xorg.conf for the resolution to be 1280 x 1024 instead of the
> current 1600 x 1200? Display is a Dell M991 and the Video Card is
> shown as Nvidia NV11 (GeForce2 MX/MX400).  CentOS 5.2 (32 bit) fully
> updated.   TIA!
>

The "nv" driver is not very good. From  your writeup, it is not
apparent if you ever get the resolution you want.  If it never works,
I suspect you are up against the limitations of nv itself.  On my
systems, it is really really limited, plus there is no 3D support.
If you are willing to use the proprietary (but free of cost) Nvidia
driver (http://www.nvidia.com), you will likely be happier.  It
includes a GUI settings thing called nvidia-settings and it also
supports xrandr.

The nvidia driver has a long README file and in my experience it is
one of the better manuals for no-cost software.

I have *not* found an up to date RPM for the nvidia driver for Centos,
and so it appears to me the only feasible route is to run the script
installer on www.nvidia.com.  That's bad because it steps on some
files you might want back later.  One main purpose of rpm.livna.org
was to keep up to date on the rpms for nvidia, but it appears to me
that the transition to the rpmfusion network has let some things fall
through.  Last I checked, rpmfusion was a few editions behind on the
nvidia driver, even for Fedora linux, and they were never very
interested in helping Centos/RedHat.   (I keep thinking I built an
nvidia RPM myself, but I can't find it today).

However you install it, that nvidia comes with a program
'nvidia-settings' and that helps quite a bit to see what you are up
against. It is like system-config-display, sorta, except that it does
not look like crap and it actually lets you see settings and
information on the system.

I've not had the trouble you report that system-config-display refuses
to do anything while logged in, incidentally, but that is pretty easy
to fix.  You can google for "boot into runlevel 3" or other ways of
getting to a "virtual terminal" after turning off the X display (in
the old days, it was /sbin/telinit 3 as root would close X entirely.
Maybe Alt-Control-F2 (any F1 through F7 is OK on Centos).

You may not need to do any fancy customization to get nvidia to work.
Just change the xorg.conf to replace "nv" with "nvidia".  nvidia
requires a kernel module, and that has to be rebuilt when the kernel
is updated.  On the Fedora systems here, I think the dkms framework is
used to automatically build that kernel module when a new kernel
starts.


Right now I'm using an Ubuntu machine (because RedHat/Centos lag too
far behind the software curve for me to do my development work), but i
believe the xorg.conf I'm attaching would work on a Centos system that
has the nvidia driver.  I want a resolution of 1400x1050, which I can
get with the windows nvidia driver on the same laptop, so I know it is
possible.  However,  that mode is lacking from the linux side.  So it
is necessary for me to stop the card from guessing EDID frequencies of
the laptop display, and I have to create modelines that allow the card
to show the resolution I want.

If you keep fiddling with settings and you find your resolution is
always "stuck" where you do not want it, then it means that your video
card is looking at the EDID frequencies of your display and refusing
to send the signal you want.

Sorry, didn't mean to start writing a book.  I've wrestled with these
so long that it is starting to seem like i should make a career out of
it.

pj









> # Xorg configuration created by system-config-display
>
> Section "ServerLayout"
>        Identifier     "single head configuration"
>        Screen      0  "Screen0" 0 0
>        InputDevice    "Keyboard0" "CoreKeyboard"
> EndSection
>
> Section "InputDevice"
>        Identifier  "Keyboard0"
>        Driver      "kbd"
>        Option      "XkbModel" "pc105"
>        Option      "XkbLayout" "us"
> EndSection
>
> Section "Device"
>        Identifier  "Videocard0"
>        Driver      "nv"
> EndSection
>
> Section "Screen"
>        Identifier "Screen0"
>        Device     "Videocard0"
>        DefaultDepth     16
>        SubSection "Display"
>                Viewport   0 0
>                Depth     24
>        EndSubSection
>        SubSection "Display"
>                Viewport   0 0
>                Depth     16
>                Modes    "1600x1200" "1600x1024" "1440x900" "1400x1050" "1280x1024"
> "1280x1024" "1280x960" "1280x960" "1280x800" "1280x800" "1152x864"
> "1152x864" "1152x768" "1152x768" "1024x768" "1024x768" "800x600"
> "800x600" "640x480" "640x480"
>        EndSubSection
> EndSection
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>



-- 
Paul E. Johnson
Professor, Political Science
1541 Lilac Lane, Room 504
University of Kansas
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