[K12OSN] Managing screen resolution

Gideon Romm ltsp at symbio-technologies.com
Thu Oct 22 22:15:06 UTC 2009

Hi, everybody.  I figured I would chime in on forcing video modes.  In
part, it depends upon what version of LTSP5 you are using, but I will
talk about things in the most recent sense.  

Oh, also, anyone using "i810" for an intel card on a modern Linux
distro, probably shouldn't.  "i810" was abandoned in favor of the
"intel" driver.  But, that's just a side point.  Also, not that "vesa"
only has "vesa" modes, so no widescreen options, no matter how much you
try to force it.  So if its a widescreen resolution you're after, best
not to use "vesa".

Now, onto forcing video modes...

In the latest version of LTSP5, by default, we look towards the video
drivers' "Xrandr" capabilities to adjust the screen resolution.  For
those of you unfamiliar with Xrandr, it is a mechanism supported by most
drivers to adjust video settings on the fly, without restarting the
Xserver or hardcoding settings in the Xserver configuration file.  To
wit, there are a set of lts.conf variables prefixed with XRANDR_, such

XRANDR_MODE_0 = "1024x768"

(check the docs for a complete list of XRANDR_ variables for lts.conf)

So, this is the preferred way of setting the mode.  If Xrandr cannot set
the specified mode, it will fall back on the driver default, which is
considerably more graceful than not starting the Xserver at all.

If you find that you don't get the mode you want with the above setting,
it may be because the mode cannot be achieved by the driver with the
auto-detected sync frequencies for the attached monitor.  So, you may
want to force:

X_HORZSYNC = "30-100"

(substituting the above ranges for those for the attached monitor).

If you still cannot get the mode, you can fall back on not using Xrandr
at all, and go back to the old way with:

X_MODE_0 = 1024x768

If this still does not result in the desired mode, best to get a shell
on the thin client itself, and look at the thin client's log file
in /var/log/Xorg.*.log to see why the driver failed to give you the mode
you requested.

Hope this helps,


PS: Of course, all of the above can be done on a per-workstation basis
by putting the parameters in the appropriate MAC-address-delineated
section of your lts.conf file

On Wed, 2009-10-21 at 23:14 +0530, raju VK wrote:
> But the basic question is still unanswered. 
> How to set individual clients video / graphic settings?.
> I myself is struggling to set the video for some 845G chipset clients.
> The auto detected screen /window is corrupted and is not responding.
> When I used XSERVER = i810, in the lts.conf, for the client, there is
> no window at all. on XSERVER=vesa, I getting a working screen / window
> but the resolution is only 600x480, which is not useful.
> the client was perfectly working when RH9 was installed on HDD, and
> the video driver was i810.
> As the server is using ATI card, do I require to copy / install  any
> i810 files to get it properly worked on the client.
> On Tue, Oct 20, 2009 at 9:59 AM, Almquist Burke
> <burke at thealmquists.net> wrote:
>         -----BEGIN PGP SIGNED MESSAGE-----
>         Hash: SHA1
>         On Oct 19, 2009, at 11:00 PM, Steven James Drinnan wrote:
>                 Just a thought, do the users like these resolutions or
>                 just bigger text.
>                 Maybe it would be better if you asked if they would
>                 prefer larger fonts.
>                 That way the screen resolution would be preserved but
>                 they would be able
>                 to see everything more clearly.
>         Wow, I just wanted to say that this is a huge pet peeve of
>         mine. Most users don't know and better (and frankly, in
>         windows, there isn't any good way to increase icon and font
>         sizes globally) so they just lower the screen resolution and
>         make everything bigger at the cost of making everything fuzzy.
>         -----BEGIN PGP SIGNATURE-----
>         Version: GnuPG v1.4.7 (Darwin)
>         iEYEARECAAYFAkrdPMAACgkQxWV7OPa/g5E3BwCfdDTli0h/KRngIgLMs7yBuMsD
>         VBsAn10bbKxicfvful2qQv1ysacY6ZhL
>         =TMN8
>         -----END PGP SIGNATURE-----
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Gideon Romm | Proud LTSP Developer
ltsp at symbio-technologies.com

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