Graphical Applications

General Graphic Application Comments

This chapter describes the use of graphical user interfaces to bring the Linux desktop to your local machine. This gives you the ability to work with graphical applications, browse and edit files in a graphical manner that is similar to your usual work patterns, and establish remote sessions that stay alive while you disconnect from the cluster. You can of course fully log out when appropriate, but by default, the session stays alive until you reconnect at a later time. This allows you to keep interactive applications running for very long times if needed.

There are three ways to connect to Arrow to run graphic applications. These are:

• Running the NoMachine NX client
• Running the X2Go client
• Running X and using an SSH terminal client to forward the X protocol

Running NoMachine and X2Go are the most efficient because they transfer information between the cluster and the client using data compression and a special protocol to minimize data transmissions.

Note: When using the third option, you will not have a full Linux desktop on your screen. Instead, Linux applications can bring up your user interface on your client for interaction. This is much slower than the other two options, but may be useful for your specific application. In this case, all rendering is done on your client rather than on the remote server.

Let's assume that you have an X server running on your machine, and that you have the ssh command available. In that case, you would do the following:

ssh -X [email protected]
enter your password
xeyes

This last command is just for testing. You should see a set of eyes that can be moved around using your mouse. If this works, then your graphical application scan be used remotely.

Graphical Applications Using NoMachine NX

To provide for remote use of graphical applications on the cluster, we've installed NoMachine NX on the login hosts. To use it,

1. Download and install the free NX Client. (Windows users should install the optional font packages.) The NX Client uses SSH behind the scenes;
2. When you log in the first time, you'll see a window with a number of configuration options. Under "Desktop", choose "Unix", either "KDE" or "GNOME", and the appropriate type of connection you have to the Internet. (Users on the Argonne network should use "LAN".)

You should be able to use interactive GUIs with NX even over a DSL or cable connection. If you have problems, please contact us by clicking to send email or via telephone: 630-252-8224.

Terminating and Disconnecting

When you quit an NX session, you can either terminate it or disconnect from it. Terminating it will close all your running programs. If you discconnect you can reconnect later to the same session.

If you close the NX client window, you'll be given a choice of terminating or disconnecting.

Reconnecting

If you want to reconnect to an NX session, you'll have to log in to the same login node on which it was started. To do this, instead of using 'login.tracc.anl.gov' as the server host, specify the login node you want to connect to.

Problems

• You may see the error message "Error activating XKB configuration" when you start a new session. This can be ignored, but if you want to get rid of it, then: from the Applications menu, go to Preferences -> Keyboard, then the Layouts tab, and click Reset to defaults. This should only need to be done once.

• If the NX client stops working for you, log in with SSH, then try moving the .nx directory in your home directory out of the way:

cd; mv .nx .nx.bak

• If you get errors similar to this:

Warning: Cannot convert string "-*-courier-medium-r-*-*-*-120-*-*-*-*-iso8859-*" to type FontStruct

you need to install the optional font packages for Windows from NoMachine.

Graphical Applications Using X2Go

X2Go can be installed by following the instructions here.. Instructions are provided for Windows, OSX, and a number of other client OSs. It should be noticed that if you don't already have XQuartz installed on OSX, you will need to do that before installing X2Go. A general X2Go tutorial can be here.

Graphical Applications Using X

xming is a convenient and easy to install X server for Windows. However, if you're doing pre- or post-processing that requires sending a lot of graphics over the network, we recommend NoMachine NX or Z2Go because their compression of the graphics yields a significant speed advantage over X.

To install X on a Mac, refer to this site
Mac uses XQuart to implement X applications and should be installed if not alread installed on your version of OSX. To bring up the window, connect to the cluster by:

ssh -Y [email protected]