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On the GPU nodes of mistral, the freely available remote 3D rendering software VirtualGL is used in combination with TurboVNC to display and interact with the interactive 3D visualization on your local workstation. Locally, the TurboVNC client software is needed in order to connect to the system. The current version TurboVNC 2.1.1 is available for Windows, Linux and other Unix platforms: TurboVNC 2.1.1 on Sourceforge


Connection to GPU nodes via Unix/Linux

Locally at CEN and MPI-M, the necessary TurboVNC client software is already installed on all Debian Lenny 64-bit Linux Workstations administered by CIS. Just "add module turbovnc" and then start the viewer as described below.

On Linux workstations, start your locally installed VNC viewer and connect to the session with the information you have received:


In this documentation, we have used, but of course you may be given another node (such as mg101, mg102, ...).

Depending on your system and the VNC client used, you can use a dialog, or command codes to adjust the compression quality, such as:

vncviewer-encodings "tight zlib" -compresslevel 9


Connection to GPU nodes via Windows

On a Windows system, you just click on the TurboVNC Viewer icon to start the client software. As the VNC Server, specify the full hostname of the node assigned to you, for example:

TurboVNC Client


In the authentication window of the client software, which pops up after you have clicked connect, you have to enter your password.

As a Windows user, you can specify the compression for the video signal being sent to your workstation comfortably with the TurboVNC Viewer Options. Simply click on Options before you connect (Figure 8), or later press the button in the top left corner of the VNC X Desktop Window. Depending on your network connection, we recommend to use jpeg compression with moderate compression settings as shown here:



If everything works as expected, you are now provided with a Virtual X Session on mg100 with the screen resolution specified. The Remote3D rendering software VirtualGL can now be used for running any OpenGL applications, such as Avizo. You can test this by typing vglrun glxgears into a terminal window, and as a result should see a 3D gear set in motion.




Secure TurboVNC Connection: SSH Tunneling

Figure 1 shows a security warning, that explains that with the current version of TurboVNC, all of your keystrokes are transmitted unencrypted from your workstation to the VIS node. As long as you don not log into other systems from your session, this doesn’t matter. But when you intend to connect from mistral to another system via ftp, sftp, ssh, your login credentials are transmitted unencrypted and could potentially be monitored by others. So if you need to connect to other systems from your session, or you just want to make sure that the connection is secure, please follow the advice given in Figure 1 and tunnel your session via ssh:

Under Linux, you can build a tunnel that forwards your local port 5901 to by typing:

ssh -f -L 5901:localhost:5901 -N <your_user_id>

Then tell TurboVNC to connect to the local end of the tunnel:

vncviewer localhost:1

With the ssh client software PuTTy, windows users can also set up an ssh tunnel in order to securely connect to mistral's gpu nodes:

Putty ssh tunneling


After filling in the Source port (5999)and the Destination, click Add and log in in order to activate the tunnel. In this case, the port number 5999 had been chosen for the local display. Just enter localhost:5999 into the corresponding field for the VNC server to connect to your VNC session: