*** This page is continually being modified to try to keep up with newer versions of OS's and as I find better ways of doing this :) ***

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There are two ways to do this, the easy way that sometimes works and the hard way that sometimes works.  Good luck.

Most Dual-monitor Friendly Distros (and how to set it up)

Kubuntu/Ubuntu 8.04 or 8.10

sudo apt-get install fglrx-amdcccle
amdcccle

OpenSUSE 11.2

KDE Main Menu -> Personal Settings -> Display

Make your settings look the way mine do in the picture.


I think this is the only Linux distribution I've tried where dual monitors just works out of the box.  My hat off to Novell.

Less Friendly Distros (with instructions)

You should be duely warned that if you've never done this before there is a good chance you will not be able to set this up.  If you have done this before you probably will not be able to do it in under an hour.  This way is tricky because there are a few different ways to do this and there is no guarantee that they will work.  I've frequently found that even after following a step-by-step process, I still have to fiddle around and research stuff before it will work.  If you don't feel confident in your Linux and/or X11 skills, I'd strongly advise either 1 monitor or using one of the distributions listed above.  I've included several x11 conf files to be referred to at the bottom of this page.

openSUSE 11.0

Follow the directions found here.  There is a good chance you don't have to change the driver configuration. 

Ubuntu 8.04 or Kubuntu 8.10 (xrandr with some aticonfig)

I have not tried this yet, but I believe this is how you have to configure dual monitors for the newer versions of this distribution.  I'm personally still running Kubuntu 8.10 X64 because I really don't want to deal with this.  However, I've configured dual montitors this way for both of these distributions so I know it works for these.  I assume it will work for later version as well.

Make sure your proprietary ATI drivers are installed by typing:

sudo apt-get install xorg-driver-fglrx

It will either install or tell you it is already installed.

sudo aticonfig --initial=dual-head --screen-layout=right.  This made some changes to the /etc/X11/xorg.conf file but didn't actually work.  You need to change the following lines below:


     Screen         "aticonfig-Screen[0]-1" RightOf "Default Screen"
to
#    Screen         "aticonfig-Screen[0]-1" RightOf "Default Screen"


where you see something like this:

Section "Screen"
        Identifier      "Default Screen"
        Device          "Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller"
        Monitor         "Generic Monitor"
        DefaultDepth    24
        SubSection "Display"
                Modes           "1680x1050" "1280x800"
        EndSubSection
EndSection

you need to make look like this:
Section "Screen"
        Identifier      "Default Screen"
        Device          "Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller"
        Monitor         "Generic Monitor"
        DefaultDepth    24
        SubSection "Display"
                Modes           "1680x1050" "1280x1050"
                Virtual          1680 1050
        EndSubSection
EndSection

The numbers that follow Virtual should reflect the size of the monitors if they were put together.  2 1440x900's placed side by side would yield 

virtual 2880 900

If they were on top of eachother, they would be 

virutal 1440 1800
 

Now that your xorg.conf file is correct, you can run a command like the following (see below for how to modify it):

xrandr --auto --output VGA-0 --mode 1680x1050 --right-of LVDS

--right-of can be replaced with

This should print out information about all monitors connected to this computer. Included this is the indentifiers of the monitors.  You'll want to replace VGA-0 and LVDS with whatever identifiers are used.

If for whatever reason an identifer is not listed when you enter xrandr you can try these defaults:

RedHat 5.2 and I think Fedora 10

Red Hat's instructions did not work for me and I suspect also will not work for other people using ATI Graphic Cards.  Fortunately, I found a work around:

• type aticonfig. If this is not recognized then you need to download the right driver.  You can get this through yum by typing:

sudo yum install xorg-x11-drv-fglrx

• If you can't access yum for some reason you can find the driver you need here.
• When the driver is installed type:

sudo aticonfig --initial=dual-head --screen-layout=right
You may need to restart your computer here.
sudo aticonfig --dtop=horizontal --overlay-on=1

• I restarted the computer
• Restart X (restart computer or ctr + alt + Backspace.

When I was setting this up for RHEL 5.2 I found the following did not work:

• xrandr versions 1.1 or earlier, most instructions need version 1.2.  You need to upgrade xrandr to make this work.  Should be easy with the help of yum.
  
• Using KDE's display (3.5) does not work.  You can  make it clone but nothing else, even though there are options that are supposed to work.

Links

http://en.opensuse.org/Multiple_Displays_Using_XRandR
http://navetz.com/v/132/Simple-dual-monitor-setup-with-XrandR-in-Ubuntu-Linux