Sending Graphics from Remote Computers

Although it is possible to interact with the image processing software on the IU clusters simply using a terminal window and the command line, the computing experience is much more informative and richer if various graphical tools are also available. If you connect to one of the clusters from a unix/linux machine, there should not be a problem with displaying any sort of graphics on your local machine. To make some of the rest of this page clearer, in computer speak, the local machine is often referred to as a client machine while the cluster machine acts as the server.

Graphics on the IU clusters are all handled by something called X11 and the way to make your client machine display graphics from them is to make certain that your client understands the X11 protocols. This can be done in a variety of ways that are dependent on the client machine used to connect to the cluster. Virtually all unix/linux machines display graphics on their own monitors using X11 and there is generally nothing to do in order to display graphics from one of the clusters on a unix/linux client.

Using a Macintosh Client

If you are using a Macintosh as the client, you will need to do a couple of things in order to display graphics from one of the clusters:

Start the X11 Application on your Mac - The X11 Application may be listed as X11.app or XQuartz and should be part of the standard operating system on all Macs. If it is not in the Applications list, find it and download it from the Apple downloads directory. You will need to run this application whenever you want to use graphical tools on the IU clusters. It is also important to remember to start this application before you open a terminal window to the cluster.
Connect to the cluster by typing "ssh -X user_name@clusterName.uits.iu.edu" on the command line - The "-X" command line argument tells ssh to send graphics through the ssh connection. Be certain that you use a capitol X since the "-x" argument does something completely different!

Using a Windows Client

If you are using any sort of Windows machine as the client, you will need to do different things, including obtaining an X server for your Windows machine. Here are the steps needed to transfer graphics between one of the IU clusters and your client machine:

A screenshot of the PuTTY software, showing the location o the Saved Sessions for Karst.

Obtain and install an X server - When one of the IU clusters sends graphics to your client machine, there must be an X server running locally to interpret the graphics. There are many different ways to do this using Windows software, and it is possible that your Windows machine will already have an X server. For example, if you are running cygwin, there is likely to be an X server already installed. It may also be the case that you are running Hummingbird's Exceed (available in some departments through IUware Online). In these cases, you will need to remember step 3: start the X server whenever you want to use graphical tools on one of the IU clusters.

If you do not already have an X server, a product called Xming is available for download. This fully functional X server will handle most of the graphics that the IU clusters will send to your client machine and is a very good solution to this problem.
Configure the ssh software to transfer graphics through the ssh connection - This will again depend on your ssh software. The following description applies specifically to PuTTY (also available through IUware Online), but the configuration of other ssh software such as SSH Secure Shell Client or SSH Tectia will be quite similar.

Start PuTTY and either edit your existing saved session for the cluster or create a new one. Before loading or saving this connection, highlight the word "X11" by following the Connection -> SSH -> X11 path in the left-hand panel of the PuTTY Configuration window. This will display a new panel on the right-hand side of the window.

Check the "Enable X11 forwarding" check box. You should not need to supply an "X display location," change the default authentication protocol or deal with any of the other options dealing with SSH and/or the Connection components. Finally, return to the Session menu and save (or resave) the modified session information.
Start the local X server - This is usually as simple as clicking on an Xming or Exceed shortcut. You should not need to configure the local X server.
Connect to the IU cluster - Using the software you configured in Step 2

Sending Graphics from Remote Computers