Remote Unix Desktop

The remote Unix Desktop is used for remotely accessing experimental and computational resources at SSRL. This is a client/server application: the free client needs to be installed on the user's home computer. The user will then be able to run all command line and X-Window based applications available at the macromolecular crystallography beam lines from that computer. The server side runs on an SSRL computer and it performs the bulk of the computational work. The client require minimal CPU and memory resources on the client computer. Only 20 kbps of network bandwidth is required for excellent performance.

The users access the beamline computers via a Linux desktop (NX client), which provides the same computing environment found at the crystallography beamlines, including access to the data processing servers (BLCPUs) and the beamline control software (Blu-Ice).

NX clients are available for Linux, Windows, Mac OS X and Solaris.

Server status

We are currently running two servers for remote access, smbnxs1.slac.stanford.edu and smbnxs2.slac.stanford.edu. Both servers are running version 3.3.0 of the NX Server software on RedHat Enterprise Linux 4.7 x86_64 operating system.

Client installation

Before accessing the NX Linux desktop for the first time, the user must follow a simple procedure to install and configure the NX client. See:

NX installation and configuration.
A video tutorial describing downloading, installation and configuration of the NX client on a Windows XP machine is also available.

Troubleshooting

Check that you have the latest version

NoMachine updates the NX Client packages several times a year. These updates usually fix real bugs and adds some features. If you have trouble with the NX Client, please check that you are running the latest version. The current version of the client is 3.3.0-6 for all platforms and it was released in January 2009.

An error occurred while connecting to the server computer

Check that you network connection is active.
Check for typos in the server name: smbnxs1.slac.stanford.edu or smbnxs2.slac.stanford.edu
Occasionally an NX server may be down for maintenance and upgrades. If smbnxs1 does not respond, try reconfiguring your client to connect to smbnxs2 instead, or vice-versa.

The NX Client session opens but then immediately closes

The client may be trying to re-connect to a previous session that is in damaged state. Although the NX Client software has a feature that allows you to kill sessions via the "NX Session Administrator", it sometimes does not work. In addition, sometimes the software will not allow you to open a ''new'' session, but automatically reconnects you (and others using the same account) to the hung session. You can try to connect to the NX server using ssh and search for running sessions as follows:
1. ssh smbnxs2.slac.stanford.edu (or smbnxs1.slac.stanford.edu)
2. List the running NX client sessions : ps -fe | grep $USER | grep nxagent
3. Kill the nxagent process: kill -9 "process_id"
If this still does not allow you to open a new session, contact support staff.

Opening a second NX client kills the first session

You may have configured the client with the same "Session Name" on two different computers. Accessing the same server with the same account and "Session Name" will terminate the first session. Reconfiguring your NX client and provide a different session name, for example include the hostname in the "Session Name".

The client session suddenly closes

Check the status of you Internet connection. Even relatively short interruptions in connectivity can cause the session to disconnect. Normally you should be able to re-connect as soon as connectivity is re-established.
Someone else in your group may be accessing the same server using the same session name as you. See the item above.

The fonts do not look correct

If you are using Microsoft Windows client, check NoMachine's website to see if there are additional font files to download.

Windows Vista problems.

The NXwin.exe process may end up using 100% cpu time or even crash and prevent the NX session from starting, the latter problem seems to be specific to 64bit Vista. The workaround is the same for both issues.
1. Disable the use of DirectDraw for screen rendering. This setting is found under the "Advanced" tab in the configuration. See the NX installation and configuration for instructions.

Mac OS X problems

Tab completion in a shell window activates "window cycling" feature. This function is normally mapped to the Alt-Tab key combination but is triggered by a simple Tab under OS X. The solution is to disable the mapping of Alt-Tab to window cycling.
1. Right click on the desktop to get the menu
2. Under the "Settings" sub menu, select "Window Manager Settings"
3. Select the "Keyboard" tab and Click on the "Add" button to create a custom keyboard theme
4. In the dialog box, give the theme a name e.g. "Mac"
5. In the "Windows shortcuts" pane, scroll down to "Cycle windows" item and double click
6. A dialog box comes up, select "No shortcut"
7. Click "Close" to get out of the config, and windows cycling is now disabled.
OS X 10.5.7 on the Intel platform have problems connecting.
- Several people have reported having trouble connecting after upgrading to version 10.5.7. The error occurs while establishing the connection, before the user is authenticated. An error message is displayed as "Connection Time Out", and the detailed error message looks like this;
```
    NX>  203 NXSSH running with pid: 849
    NX>  285 Enabling check on switch command
    NX>  285 Enabling skip of SSH config files
    NX>  285 Setting the preferred NX options
    NX>  200 Connected to address: 134.79.28.89 on port: 22
    NX>  202 Authenticating user: nx
    NX>  208 Using auth method: publickey 
```
- At least one user have reported that Starting the Mac's X11 software manually before starting the NX client solved the problem.
- A test with a fresh install of OS X 10.5.7 and the latest NX client 3.3.0-6 did not show this problem.

Access to beamline computing facilities

After logging in to the NX server, the user may establish a remote internal connection to any SSRL SMB computer:

Click on the Blu-Ice icon in the menu bar to open Blu-Ice.
Click on the SSRL icon to open a BLCPU computer to process your data.
Open a terminal window by clicking on the terminal icon or right-click anywhere on the desktop window and select a terminal from the menu.
Log in to any desired machine as described in the computing environment document.