Today I'm going to show you how to install xdmx. Basically it will allow you to use an old laptop as an extra monitor. It can also be used to make huge tiled displays. Lets say you want a 16 monitor display. You can't fit 16 video cards in your machine, so how would could you do that...with xdmx!
First thing you want to do is install xdmx on every machine that you are going to use, for me its my main workstation and my old laptop. The problem is that the xdmx package that is in the ubuntu repositories is broken, it throws seg faults left and right. So go here http://packages.debian.org/etch/xdmx and download xdmx.
Install it with
sudo dpkg -i xdmx_1.1.1-21etch5_i386.deb
To run xdmx securely you are going to want to run it through an ssh tunnel. You can also run xdmx by turning on X11 tcp listening but this is a huge security hole. It will allow anyone on your network to see every keystroke you make in an X environment. So on the computer that you are going to use as the xserver (my workstation) you need to have an ssh-server installed.
sudo apt-get install openssh-server
Now from my old laptop (your second display) ssh into your main workstation. To make things faster use a blowfish cypher.
ssh -X -c blowfish-cbc user@maincomputer
Now type:
export |grep DISP
you see something similar to this: (the numbers might be different)
paradox@griver:~$ export |grep DISP
declare -x DISPLAY="localhost:10.0"
Now you need to start an xdmx xserver. You need to run the command on the main workstation but from the laptop. So from your ssh shell run:
startx -- /usr/bin/Xdmx :1 +xinerama -display :0.0 -display localhost:10.0 -norender -noglxproxy
the startx -- /usr/bin/Xdmx starts and Xdmx xserver. The :1 is the display number. If you are already running a desktop it is probably on :0. +xinerama makes both computers act as a giant screen. The first -display :0.0 is the display for your main machine and the second is the display for the old laptop. The -norender and -noglxproxy makes everything render smoothly, but it will prevent you from running openGL stuff and you wont have any graphic effects. I had to do this because my laptop has and ATI card and my workstation has an NVIDIA. It they both have a similar card you probably don't need these.
That's it, a new desktop should popup and you should have super cool duel monitor setup.
