Graphical linux desktop access using NX

This article explains how to connect to a graphical linux desktop within the JASMIN environment using NoMachine NX. It explains:

  • how using a JASMIN-side graphical desktop can improve performance
  • how to set up your connection using the NX enterprise client
  • how to log in and use a graphical desktop session

Note: This is a new service - make sure you read the instructions carefully and bear with us in the case of any teething problems.

Introduction

Using X11 graphics over a wide-area network can be very slow, and is not recommended or supported on JASMIN. NX helps by providing a graphical desktop within the JASMIN environment, instead of on the end-user’s local machine at the end of a wide-area network path from JASMIN. A small client application available for you to install on your local machine enables you to connect to specific servers within JASMIN but send graphics output across the network in compressed form, resulting in much better performance.

This provides an improved user experience compared to that offered by the alternative X2GO system previously offered on JASMIN, and is recommended over standard X11 graphics.

The following "special" login servers have the NX service available and can be used as described below: 

  • nx-login1.jasmin.ac.uk
  • nx-login2.jasmin.ac.uk
  • nx-login3.jasmin.ac.uk

Note: In all other respects these are the same as the standard login servers, but should only be used by users connecting with the NX enterprise client as described below. Please do not use them for standard terminal-based SSH connections as this preserves system resources for their intended purpose.

Installing the NX enterprise client

Download the NX client (Enterprise edition) from https://www.nomachine.com/download-enterprise

Versions are available for Windows, Mac and Linux. You may need privileges on your local machine in order to install the software so you may need to ask for help from your local IT helpdesk.

Note that the "enterprise" edition of the NX client is different to the "standard" edition available from the more publicised download link on the NoMachine website: the standard edition contains additional server components to enable remote access to your own machine: perhaps convenient but not something we would recommend by default. The enterprise edition is purely a client to connect to a remote server, which is what we're trying to achieve here to access JASMIN.

Remember to check for updates for the enterprise client to ensure you always have the latest stable version. You can configure the application to check for updates (and optionally apply them automatically) by going to Settings / Updates in the menu.

Setting up your connection

The instructions below are very similar for Mac / Windows / Linux, once the enterprise client is installed.

  1. Open the NX client
  2. In the "Recent Connections" window, click "New"
  3. Select "SSH" (rather than "NX") protocol in the pull-down list, click Continue
  4. Enter the name of the host as nx-login1.jasmin.ac.uk (or one of the other machines listed above) and leave the port as 22. Click continue.
  5. Select "Private key" for the authentication method, tick the box for "forward authentication" and click Continue.
    1. Please do not use "Authentication agent" as the authentication method: this may not work universally so is not supported.
  6. Select "Don't use a proxy", click Continue
  7. Edit the name of the connection if you wish, click Done

Connecting

  1. Select the connection profile which you just created (by default it will now be highlighted). Click Connect
  2. Enter your JASMIN username and passphrase. Click OK
  3. Select "Create a new virtual desktop", click Continue
  4. Note the instructions for how to reach the NX menu once in the session, and select screen settings from the list of icons: Recommended setting is "Fit to window" (leftmost icon)
  5. Click OK on this and subsequent screens giving information about the NX and desktop environments.
  6. You should be presented with a linux deskop on  nx-login1.jasmin.ac.uk 

Using the graphical desktop environment

Once you have set up the environment to your liking, you can try connecting to other systems within JASMIN such as   jasmin-sci1.ceda.ac.uk and using a graphical application such as the firefox browser or simply  xclock.

  1. Click "Activities" (top left menu on desktop)
  2. Click the Terminal icon
  3. Try an onward SSH connection
    $ ssh -AX jasmin-sci1.ceda.ac.uk

    (you may find -AY works if -AX does not).

  4. To see the list of sci servers which is normally presented at login (which helps in selected a less-loaded sci server), type the following:
  5. $ cat /etc/motd
  6. Try opening a simple graphical application on jasmin-sci1.ceda.ac.uk  with the command:
  7. $ xclock

    You could also try opening the firefox browser with the firefox command. This sometimes takes a little longer to initiate so xclock can be a quicker test. Cancel the graphical application (xclock) with CTRL + c, or use the application's own exit command, if it has one.

  8. To log out of the virtual desktop, locate the menu top-right, and select your name, then "Log Out"
  9. Notes:

  • The number of "virtual desktops" which can be created per user is limited to 1 in order to preserve system resources.
  • Although in theory sessions and desktop windows should persist when you close down the NoMachine client and when you re-open it to the same connection, you should not rely on this feature.

Troubleshooting

  • After the first connection, subsequent connections to the desktop sometimes have some symbols keys e.g. @ and " transposed. We are aware of this and are currently seeking a solution.
  • Please do not try and connect using the proprietary "NX" protocol. Select "SSH" as the protocol.
  • Please use "Private key" as the authentication method, not "Authentication agent", as the former has been found to work more consistently and reliably, particularly for onward connections to other machines.
  • Make sure you have installed and are using the most recent version of the NoMachine Enterprise Client.

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