Here is a description and image from the Synergy site which demonstrates this functionality:

In this example, the user is moving the mouse from left to right. When the cursor reaches the right edge of the left screen it jumps instantly to the left edge of the right screen.

You can arrange screens side-by-side, above and below one another, or any combination. You can even have a screen jump to the opposite edge of itself. Synergy also understands multiple screens attached to the same computer.

I’ve been using it for a couple of years now and I find it an invaluable addition to the arsenal of any developer who works in both Windows and Linux. I built a new computer over the weekend and finished installing Ubuntu 8.08 Gutsy Gibbon tonight. One of the first things I did was install Synergy. Previously, I set it up on Red Hat Enterprise, but either way, the set up is pretty straightforward.

Let’s get started installing Synergy, shall we? The Windows set up is easier because it has a GUI. In Windows, go to the Synergy SourceForge page to download the latest release (version 1.3.1 as of this writing). Here’s the download link if you don’t want to be bothered with navigating the SourceForge page:

• Download SynergyInstaller-1.3.1.exe from SourceForge

Once it’s downloaded, install it and open the synergy.exe file to launch the program.

I prefer to set Windows as the client and Linux as the slave, although it was recommended in a forum post to do the opposite in Windows Vista. Regardless, I haven’t had issues with Vista or XP in either configuration.

For now, let’s assume your keyboard and mouse is hooked into the Linux box and you want to make Windows the slave (client). To do this, simply click the radio button next to Use another computer’s shared keyboard and mouse (client). Then, enter the Linux computer’s host name next to Other Computer’s Host Name. For me, this is ‘ubuntu’ but you may have been more creative with your host name.

We’re not quite ready to test it yet, so leave this window open and go back to Linux for a moment. In Ubuntu, install Synergy by typing:

sudo apt-get install synergy

If you prefer doing things in the console, then you can manually create the config files. Otherwise, you can use a GUI called QuickSynergy to get up and running. Here’s how to do either way:

The manual way might take a little longer, or not, depending on how good you are with command line interfaces. To install it manually, first you must create a configuration file called synergy.conf that looks like this:

    section: screens
      screen1:
      screen2:
   end
   section: links
      screen1:
          right = screen2
      screen2:
          left = screen1
   end

You can place the config file in /etc/ or /usr/local/etc/ (whichever you prefer). Just make sure it is somewhere in the environment PATH for convenience’s sake.

For me, this file says:

    section: screens
      ubuntu:
      laptop :
   end
   section: links
      screen1:
          right = laptop
 screen2:
          left = ubuntu 
   end

My laptop is, of course, named ‘laptop’ — again, feel free to use more imaginative names (as long as it is actually the name of the computer). It isn’t necessary to use the name of the computer as the name of the screen but it requires extra configuration otherwise. (See the official documentation for more information on this).

Now that you’ve created the file, you’re ready to launch Synergy. Give it a try with this line:

    synergys -f --config synergy.conf

Assuming it starts correctly, jump back to Windows and click ‘Test’ in Synergy there. It should say that it connected OK and everything is fine and dandy. If that’s the case, then just click ‘Start’ and you’re done. If not, visit the docs page and scroll towards the bottom to troubleshoot the issue.

If you prefer graphically configuring Synergy, that’s an option, too. I guess I should have put the GUI solution first for us lazy developers, but it’s good to be familiar with the non-graphical way anyway. I know that I managed to mess up my config file using the GUI and had to dive in to it regardless.

That being said, the GUI (called QuickSynergy) is very straightforward and easy to use. To install QuickSynergy, type the following in a Linux terminal:

sudo apt-get install quicksynergy

Once it’s installed, you can type quicksynergy to launch it (add & at the end if you want to retain your terminal window) and a window will popup that allows you to configure Synergy, either as host or client.

The default tab which opens is for host, and all you have to do is enter the correct screen names and then start it. For me, my Linux desktop (named ‘ubuntu’) is on the left and my Vista laptop (named ‘laptop’) is on the right, so I just made sure that the fields to the left and right of the computer image said ‘ubuntu’ and ‘laptop’, respectively.

QuickSynergy is theoretically easier to use than the command line way detailed above, so I won’t go into much depth here. If you get stuck with QuickSynergy, either try the command line way, or visit the QuickSynergy SourceForge site to see screenshots and example configurations.

Extra Features:

• Synergy has the ability to auto-sync starting and stopping of screensavers
• You can copy and paste between Linux and Windows (this is a huge time-saver!)
• Easily lock the mouse/keyboard to the current screen by toggling scroll lock (assignable to any other key)