Re: [gdm-list] Multiple monitor issues w/ GDM 2.28

[Ray Strode <halfline gmail com>]

Hi,

On Thu, May 13, 2010 at 12:36 AM, Lawrence Statton <lawrence cluon com> wrote:
> I'm having some issues getting my multi-headed configuration working.  I'm
> migrating from a failed Sun E2 to PC hardware running Linux.
>
> I am trying to get a single display configured with three screens.  (I use
> the words 'screen' and 'display' in their X meanings  - that is:  One X
> server at :0 is handling three screens :0.0, :0.1 and :0.2 )
>
> I've gotten to the point where I have X driving two of the three monitors
> (after buying 4 different frame buffers) but I only get useful behavior on
> one of the monitors ( I suspect very strongly I can get the three-headed X
> server going - all signs are pointing to "yes" but the 3rd display is
> temporarily in use by another person here )
>
> OS is recent Ubuntu (10.04 LTS) and thus far everything is stock out of the
> box *except* that I've
> got a custom xorg.conf
>
> I've got two frame buffers -- one is a Radeon Dual-VGA PCI card (9000
> series, I don't have the exact part number at hand) which is driving the
> 'less useful' monitor
>
> The computer has video on the motherboard (it's an IBM/Lenovo ThinkCentre -
> Intel 915G chipset) which is driving the 'more useful' monitor.
>
> The machine boots and the 'mostly purple' Ubuntu root-window graphics appear
> on *each* screen, but only one of them has any "real activity" (that is:
>  When I log in, there are only window-manager decorations in the :0.0
> screen, only the :0.0 screen responds to clicks in the root-window) ... I
> can mouse over to the other screen and see the pointer.
>
> If I try launching an X client (e.g. xterm -display :0.1 ) "nothing appears
> to happen" ( no error returned, but neither does a terminal launch ) (nb I
> also tried launching the xterm as root, in case there were some permission
> issues )
This actually has nothing to do with GDM.  It's an X configuration
question, which would better be asked on the X list or maybe the
ubuntu support forums since you're using ubuntu.

Note though, that multiple screens (called "zaphod mode") has gone out
of fad in the last 6 or 7 years and support for it has been spotty, so
you may not have much luck.  Or given the right xorg.conf you might be
able to get it to work.  Not sure.  Anyway, the X list would probably
be able to help more.

> The release notes mention that  "GDM 2.20 and earlier supported the ability
> to manage multiple displays with separate graphics cards" and "These
> features were not added back during the 2.22 rewrite."
> The question looming large in my mind is:  Are they using the words
> "multiple displays" in the pedestrian sense of "many things on my desk" or
> in the specific X sense of the word "a group of screens bound to a keyboard
> and mouse"?
I think this is about starting multiple statically configured login
screens on separate X servers in one machine at the same time. Not
sure.

> Can gdm/gnome be made to do what I want, or am I going to just have to
> continue using xdm/fvwm like I have been for the last 15 years?
I don't think the display manager has anything to do with your
problem, so I don't think going back to xdm/fvwm would help.  Of
course, you're free to try and if that environment is what you're most
familiar with then you might be ultimately more happy sticking with it
anyway.

--Ray