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 the remote use of graphical applications on the cluster, we've installed NoMachine NX on the login hosts. This method allow you to establish a remote desktop on the login machine, which stays alive even when you disconnect from it. You can of course log out of that connection, but by default, the desktop stays alive, allowing you to keep interactive applications running while disconnected. To use this software,

• download and install the free NX Client.
• connect to the TRACC cluster using one of the login nodes:
  • login1.arrow.tracc.anl.gov
  • login2.arrow.tracc.anl.gov
  • login3.arrow.tracc.anl.gov
  • login4.arrow.tracc.anl.gov
• The NX protocol for connections is not supported. Please choose SSH from the pull-down menu.
• When connecting the very first time, you are prompted to confirm that you are connecting to the correct server, showing a server key. Confirm and continue.
• When doing this for the first time, create a new Linux Desktop. This will be shown in the future when connecting again.
• Please remember that you need a proper account, password, and that we need to have your public IP address on file for all of this to work properly.

If you have problems, please contact us by clicking to send email or via telephone at 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 disconnect, you can reconnect later to the same session. Interactive applications will continue running while disconnected, so this is a convenient way to occasionally check on progress, or to work with long running applications despite possible network issues.

If you close the NX client window, you will be simply disconnected and can resume this connection at a later time. To fully log out, use the Linux pull-down command at the top left of your screen, and choose the bottom entry to log out.

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.

Problems

We will post trouble-shooting instructions in this section if ever needed. The latest versions are very stable.

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.

After installing the client software, create a new connection with the following settings

• connection to one of our login servers
  • login1.arrow.tracc.anl.gov
  • login2.arrow.tracc.anl.gov
  • login3.arrow.tracc.anl.gov
  • login4.arrow.tracc.anl.gov
• account name and password of course
• IMPORTANT: from the pull-down menu, choose the XFCE desktop
• Also, we recommend turning off remote audio (it won't work anyway)

• on Macs: 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 way to install an 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 X2Go because their compression of the graphics yields a significant speed advantage over X. Also, rendering is generally perform on the server side rather than your local machine, speeding things up. In addition, the X protocol is very chatty, and performs poorly over the SSH encryption channel.

• To install X on a Mac, refer to this site
• The 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 using the following (-X or -Y is required):

ssh -Y [email protected]