Note: The commands and utilities in this article have been tested on a Debian Cloud Server. They are not guaranteed to function correctly on other distributions. However, the General Package Installation Guidelines article may assist in "porting" this article to another distro.

What is X?

X (or X11) is short for the X Window System, a framework for providing a graphical user interface (GUI), primarily used in Linux. X uses a client/server model; a client application displays its graphics on an X server. This means that, before you can run X over SSH, you will need to install X libraries on both your Cloud Server and your local machine. This article will briefly summarize how to do this.

X Client

The X client libraries may be installed using your system's built-in package manager. On a Debian server, the required libraries will be installed as dependencies the first time you attempt to install a graphical application. For instance,

aptitude install xterm

will install xterm along with libXaw and several other libraries. (Xterm is a graphical terminal application.)

X Server

The X server libraries depend on the operating system installed on your local machine. If you're using Mac OS X, you shouldn't need to do anything -- the required libraries are already installed! (In the off-chance that they aren't, you will want to install XCode from your system discs.) If you're using Linux, there's also a good chance the relevant libraries have been installed. For example, the popular desktop managers such as GNOME and KDE rely on X; if you're using them, you're using X also. Windows, on the other hand, will require a specialized X Window Server such as Xming. Installing an X server on your local machine is beyond the scope of this article, but once this step is completed, there's only one thing left to do...

Connect to X over SSH

Running a graphical program is not much different from running any other tool on the command-line. The only real difference is in how you connect (and that difference is small):

ssh -X user@1.2.3.4

Notice the "-X" switch? That tells SSH to allow X forwarding so that the X client on your Cloud Server may connect to the X server on the local machine. Once inside, let's test out the xterm application we installed:

xterm

Voila! An xterm window appears on the local machine, nicely integrated with our own desktop. You've just tunneled X over SSH, and can now easily run graphical applications on your Cloud Server without a desktop manager. Now go explore the possibilities!