Graphic Environment

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For graphical pre- and post-processing purposes some visualisation nodes have been integrated into the vulcan cluster. The nodes are equipped with a nVIDIA Quadro 5800 FX with 4GB graphics memory, 1 quad core CPU and 24 GB of main memory. Access to the nodes is possible by using the node feature visfx.

user@cl5fr2>qsub -I -l select=1:node_type=visfx -q vis

To use the graphic hardware for remote rendering there are currently two ways tested. The first is via TurboVNC the second one is directly via VirtualGL.

VNC Setup

If you want to use the vulcan Graphic Hardware e.g. for graphical pre- and post-processing, on way to do it is via a vnc-connection. For that purpose you have to download/install a VNC viewer to/on your local machine.

E.g. TurboVNC comes as a pre-compiled package which can be downloaded from For Fedora 13 the package tigervnc is available via yum installer.

Other VNC viewers can also be used but we recommend the usage of TurboVNC, an accelerated version of TightVNC designed for video and 3D applications, since we run the TurboVNC server on the visualisation nodes and the combination of the two components will give the best performance for GL applications.

Preparation of vulcan Cluster

Before using vnc for the first time you have to log on to the Nehalem frontend and run


which creates you a .vnc directory in your home containing a passwd file.

Starting the TurboVNC server

To start a TurboVNC server you simply have to login to the cluster frontend via ssh.


Then load the VirtualGL module to setup the VNC environment and launch the VNC startscript.

user@eslogin001>module load tools/VirtualGL

This will set up a default VNC session with one hour walltime running a TurboVNC server with a resolution of 1240x900. To control the configuration of the VNC session the script has three optional parameters. [walltime] [geometry] [x0vnc]

where walltime can be specified in format hh:mm:ss or only hh.

The geometry option sets the resolution of the Xvnc server launched by the TurboVNC session and has to be given in format 1234x1234.

If x0vnc is specified instead of a TurboVNC server with own Xvnc Display a X0-VNC server is started. As its name says this server is directly connected to the :0.0 Display which is contoled by an X-Server always running on the visualisation nodes. A session started with this option will have a maximum resolution of 1152x864 pixels which can not be changed.

There is also a -help option which returns the explanation of the parameters and gives examples for script usage.

The script returns the name of the node reserved for you, a display number and the IP-address.

VNC viewer with -via option

If you got a VNC viewer which supports the via option like TurboVNC or TigerVNC you can simply call the viewer like stated below

user@client>vncviewer -via <node name>:<Display#>

VNC viewer without -via option

If you got a VNC viewer without support of the vis option, like JavaVNC or TightVNC for Windows, you have to setup a ssh tunnel via the frontend first and then launch the VNC viewer with a connection to localhost

user@client>ssh -N -L10000:<IP-address of vis-node>:5901 &
user@client>vncviewer localhost:10000

Enter the vnc password you set on the frontend and you should get a Gnome session running in your VNC viewer.

GL applications within the VNC session with TurboVNC

To execute 64Bit GL Applications within this session you have to open a shell and again load the VirtualGL module to set the VirtualGL environment and then start the application with the VirtualGL wrapper command

vglrun <Application command>

Vgl in vnc session.png

GL applications within the VNC session with X0-VNC

Since the X0-VNC server is directly reading the frame buffer of the visualisation node's graphic card, GL applications can be directly executed within the VNC session without using any wrapping command.

Ending the vnc session

If the vnc session isn't needed any more and the requested walltime isn't expired already you should kill your queue job with

user@cl5fr2>qdel [Job ID]

Usage under Windows

VNC viewers for Windows often do not support the '-via' option to tunnel via SSH. In this manual tunneling is required, which can be done using the PLink tool which comes with the [[1] distribution.

Open a command prompt window and run PLink with the options

plink.exe -N -L 10000:<IP-address of vis-node>:5901

The you can need to start your VNC client and connect to the address localhost:10000.

VirtualGL Setup (WITHOUT turbovnc)

To use VirtualGL you have to install it on your local client. It is available in the form of pre-compiled packages at


After the installation of VirtualGL you can connect to via the vglconnect command

user@client>vglconnect -s

Then call the prepare the visualisation queue job and connect to the reserved visualisation node via the vglconnect command

user@cl3fr1>module load tools/VirtualGL
user@cl3fr1> XX:XX:XX
user@cl3fr1>vglconnect -s n150701

where XX:XX:XX is the walltime required for your visualisation job.

On the visualisation node you can then execute 64Bit GL applications with the VirtualGL wrapper command

user@vis-node>module load tools/VirtualGL
user@vis-node>vglrun <Application command>