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[K12OSN] Dual monitors on single client?



> I would like to know if anyone has put dual video cards for dual monitors on
> one client, either as a mirrored screen, or extended screen.  I'm not picky.

I've never done that on a thin client, but I've been running
multi-head workstations for years, some with Xinerama and some
without.

Just buy a single dual-head video card or add a second (PCI, probably)
video card to your system.  Then...

The trickiest part is figuring out your X server configuration,
because that's where you identify your video adapters, monitors,
resolution(s), color depths, and head orderings.

I've tossed my xorg.conf (/etc/X11/xorg.conf on my Ubuntu system,
xorg.conf sometimes shows up in other places, such as /etc/) up at
http://majen.net/docs/xorg.conf in case it is a helpful example.

Here are the important things to note:
1. I have two "Device" sections.  Each of these refers to a video
   adapter, and note that I identify the PCI BusID for each.  You can
   find this number with the 'lspci' command.  Here are the relevant
   lines from my 'lspci' output:
   0000:01:00.0 VGA compatible controller: nVidia Corporation NV34
   0000:00:0c.0 VGA compatible controller: nVidia Corporation NV34

   Note that from the above output, I entered devices with BusIDs of
   "PCI:1:0:0" and "PCI:0:12:0".  (The lspci output is in hex (c=12);
   xorg.conf might be perfectly happy with hex, I don't know.)

3. I have two "Monitor" sections.  Self explanatory, I think.

4. I have two "Screen" sections.  Each screen section combines
   a Device, a Monitor, and one or more "Display" subsections that
   specify resolutions and color depths.  Realistically, if you always
   know what your configuration is going to be you can just have one
   of those subsections, and it only needs to refer to one color depth
   and one resolution.  But then if you ever plug into a different
   monitor, for example, you might not get any graphical display...

5. I have a "ServerLayout" section that tells Xorg where my screens
   are relative to one another.  If I move my mouse off the left side
   of my left monitor and it immediately enters the right side of my
   right monitor, I know this is where I need to change things.  (Or
   I could move the physical monitors on my desk... ;)

6. I have a "ServerFlags" section that turns Xinerama on.  Xinerama
   allows a multi-head display to act like one big, unified display.
   This means you can move windows from one display to the other,
   though it also means that obnoxious web-browser-resizing web pages
   can create HUMONGOUS popups from time to time, which is rather
   terrifying.

7. In every section, "Identifier" can be anything you want, as long as
   you use the same string when you refer to something elsewhere.  For
   example, I have a Device named "nvidia-1", and I have a Screen
   section that refers to "nvidia-1" for its Device.

8. Like with everything else, mucking with your X server configuration
   just takes experience.  It was all rather bewildering to me at
   first, why one thing would work and not another (usually why
   *nothing* I tried would work...), but eventually you can get the
   hang of it.

9. Based on my weak understanding of the LTSP, you'll have to put all
   this stuff in some sort of craaaaazy /opt/ltsp/i386/etc/lts.conf
   file on your LTSP server, if you want to do this on a thin client.

10. I guess I should mention the line "ZAxisMapping" in the "Input
    Device" section for the mouse.  That enables normal scrolling.

Oh - but you want to use this to *mirror* your display for a projector
- in that case Xinerama is definitely not what you want.  I've done
that, too (usually the default config for a dual-head video card), but
I always got rid of it ASAP because I didn't want it.  Google a bit
and you should find how to do that; it should just be a change in your
ServerLayout, I'm guessing.

> I however, do need to put 2 monitors on a client.  I need to be able to 
> view a web page with a matrix of 30+ security camera view at the same 
> time.  Is it as simple as adding 2 supported video cards to the same PC?

Yep, as long as you do all that other stuff I mentioned above.  ;)

--matt

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