Understanding Servers in General

[inteluser]

It's certainly possible; I have it working on mine. First, I'll explain why it's possible; see the bottom of this post for why it's not.

There are basically two ways to use a remote desktop on a VPS - X forwarding and running a window manager, or VNC.

X forwarding allows graphical programs run on the remote computer (the VPS) to be displayed on the local computer (the one you're sitting at). This is accomplished by running an X server. There are several commercial X servers available: Exceed Hummingbird is one among many, for example. It is also possible to use Cygwin, a windows-based implementation of many unix utilities, to run a free X server. If your local computer is a linux computer, you likely need do nothing; you probably already have a local X server.
X forwarding is set up using SSH. For example, using the command line, instead of typing

ssh -l user host.com

type

ssh -l user -X host.com

. If you are using a graphical SSH interface like Putty or SecureCRT, there is an option to set up X forward (alternatively called X tunneling, perhaps).
Once X forwarding is enabled and an X-server is running, any graphical programs you run on the remote computer (using the SSH command line) will appear on your screen (for example, running will have it display graphically in a window).
To have an entire desktop, you need to run a window manager. As such, you need to install a window manager. The ones most users are familiar with are KDE and GNOME. These can be installed using the "yum" command, or probably through the Virtuozzo web interface. However, these window managers are exceedingly memory intensive; you may be better off installing a window manager like ratpoison or Fluxbox - see the end of the post for why.
Once you have a window manager installed, run it through SSH while X-forwarding is enabled. With any luck, the desktop should pop up on your screen.

When you exit from SSH, the X connection will be broken, and all the X applications (and the desktop itself will terminate). If this is not what you want, you may want to use VNC.

The VNC approach has a virtual desktop running on the remote host all the time, and allows you to connect to it. The desktop is opened in a window on your computer; you control the mouse and keyboard. When you move the mouse on your computer, data is sent to the remote host telling it that you are moving the mouse, and the screen changes accordingly. If you click on something in the VNC window, that click is relayed to the other server, and whatever should happen, happens.

VNC has never had a good record of security. Everything is sent unencrypted, and strong passwords are not supported. However, the program x11vnc, when used properly, is in fact reasonably secure (secure enough, for example, that I'm happily using it). Even that, however, is less secure than the X-forwarding SSH approach, so if you can get a local X server running, and you don't need a persistent desktop, that's a better option (if you don't need a desktop, but just want graphical applications, it's a much better option).

Now, as to why this is all impossible: graphical applications tend to use a lot of memory. Large behemoth window managers like GNOME and KDE are probably right out on all but the highest-end VPS machines; low-weight window managers like ratpoison are OK (using perhaps 20M of memory). However, that's not the whole story. Graphical programs also use tons of RAM. Firefox, for example, has no problem at all chomping up 100M of RAM, and can easily go higher. There are some alternatives to this, using low-weight graphical programs, but one should be careful and do research. Using the VNC approach somewhat exacerbates this problem because the display is always there, although of course if you don't care to have a persistent display, you can kill the vnc server when you're done with it and start it up when you need it. Trying to do this with a 128M machine is probably doomed. I'm successfully doing it with a 256M machine, but I have to be careful about what I run.

Do your research and have fun.