X-Windows Acceleration Via NX

Introduction

NX is a computer program that handles remote X Window System connections and it provides two benefits for NERSC users:

• NX can greatly improve the performance of X Windows to the point that it can be usable over a slow link such as a dial-up modem.
• NX provides sessions that allow a user to disconnect from the session and reconnect to it at a later time while keeping the state of all running applications inside the session.  This gives users a virtual desktop that's running at NERSC.

Availability

NERSC has made NX available to all active users.  If you can log in to a NERSC system you can connect via NX.

Current Users (Live!)

The map below shows the connected users at this moment. Red blobs are the active users and blue blobs are the suspended connections (though the jobs might still be running).  Many users have no geographical information and they are not shown here.

Download NX Client

To use NX, you need to download the NX Client.  NX Clients for most popular platforms (Linux, Mac OSX, Solaris, Windows) are available from NoMachine's Download page.

Set up the NX Connection

To set up the NX Connection you can do one of the following:

Note: Please make sure you install the correct NX access key.  The old Franklin or Euclid NX access key will not work for the new NX server.

• Download a ready-to-use configuration file:  This is the easiest way to configure NX client.  It is optimized for the most commonly seen scenarios.  To download the configuration file please go to the NX Configuration File Download Page (login needed).
• Manually configure the NX Client:  For a detailed configuration tutorial please refer to the "NX Manual Setup Page".

Connect to the NX Server

To connect to the NERSC NX Server start the NX Client and put in your NIM Username and Password.  Then click "Login". (For NX Player 4 instructions please refer to the NX Player 4 page).

Connect to NERSC Systems

After connecting to NERSC you will see the FVWM window manager.  You can then click the "NERSC System" button to connect to a NERSC System.  You might be asked to create a new keypair or provide a password for an existing keypair.

SSH Agent and NX

The NX server acts as a gateway to all other NERSC systems.  Users access other NERSC systems via SSH.  SSH Agent is used to help simplify the authentication from the NX server to other NERSC systems so that you do not need to type a password each time a new connection is created.  You can click on the "SSH Agent" menu to manage SSH Agent behaviors.

Generating a Keypair

SSH Agent requires a keypair to function.  The first time you click an item on the "NERSC Systems" menu the keypair is created and installed.  You need to provide a password to encrypt your private key.  This password can be different from your NIM password.  You can regenerate the keypair by selecting the "(Re)generate Key Pair" menu item from the "SSH Agent" Menu.

Loading the Keypair

SSH Agent can load a keypair into memory and use it as the authentication method to other NERSC systems.  A keypair will be automatically loaded when a user tries to connect to a NERSC system via the menu.  After the keypair is loaded it will remain active until it is removed, i.e., the user can login to any NERSC system without entering a password each time.

SSH Agent Credential Removal Policy

For security reasons the NX Server will remove the loaded keypair from the SSH Agent on any of the following occasions (meaning you will need to type the keypair password again next time you connect to a NERSC System):

• You suspend or terminate the current session;
• You are inactive for 30-minutes;
• 12 hours after the keypair is authenticated (12 hrs key lifetime).

Suspending or Terminating a NX Session

When you close the NX window (e.g., by clicking the "cross" button) a dialog box will appear providing the choice of either suspending or terminating the session.

• Suspending the session will preserve most running applications inside the session intact and allow you to reconnect to the session at a later time.
• Terminating the session will kill all the running applications inside the session and all unsaved work will be lost.

If you lose your connection to the NX server (e.g., if your internet connection is lost) NX will automatically suspend the session allowing you to reconnect to the same session while keeping the running applications intact.