The first step towards dual monitors involves installing the NVidia 3D drivers. Luckily, NVidia has great Linux support and the drivers can easily be downloaded from the Ubuntu repository. Ubuntu Feisty Fawn gives users the option to install these drivers when first installing, but in case you chose not to install these drivers, all it requires is one line of code in the terminal:
sudo apt-get install nvidia-glx
Now that the drivers are installed, let's make sure that we're using them. First, let's check xorg.conf, the main location for display settings in Linux. Type sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf_backup. This ensures that we have a backup copy in case some of the settings we're about to edit break X and don't allow you to use a graphical interface! I suggest always doing thins before changing settings in Linux manually to ensure easy recovery later. Now we're ready to edit our settings, so type sudo gedit /etc/X11/xorg.conf. Under the module section, replace "nv" with "glx". Under the device heading, make sure that Driver says "nvidia". Under the screen section, add the following line:
Option "RenderAccel" "true".
Now save your changes and close gedit. We're going to reload X to ensure that we're now using the proper drivers. Reload X by hitting Ctrl+Alt+Backspace. This will require you to log back into Ubuntu, so if you're not using a browser that saves your session, like Firefox/Swifterfox, make sure you bookmark this guide to follow the remaining instructions. If our install worked, you should see the NVidia logo flash quickly before the Ubuntu log in screen comes up. Actually, if this doesn't work, you're not going to be able to load X properly. If that's the case, you're going to have to type this into the console to replace the new xorg.conf with the old:
sudo cp /etc/X11/xorg.conf_backup /etc/X11/xorg.conf
Assuming everything went well, we're quite close to having dual screens working. Let's go back into xorg.conf using sudo gedit /etc/X11/xorg.conf. Now go back under the heading "Screen". Let's add a few lines:
##This turns on NVidia's TwinView
##Here I'm setting the resolution to the individual monitors.
Option "MetaModes" "1280×1024 1280×1024"
That should be it! Restart X with Ctrl+Alt+Backspace and you should have two screens. If the orientation of the screens is off, try this under the "Screen" heading...
Option "TwinViewOrientation" "LeftOf"
LeftOf can be LeftOf, RightOf, Below, Above, or Clone.
Hope that was helpful!