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VNC redirection

If you log on to a Linux computer via the network and want to use programs with a graphical user interface (such as kprinter), you need a screen redirection. From a Linux computer you can simply use ssh -X, then graphical programs should start normally.

When logging in from a Windows computer, you can help yourself in this way:

Start VNC server

Start a new X server on the server with

vncserver -query localhost

This returns a message of the form

New 'X' desktop is host:1

or similar, where the "1" is the number of the X server, it can change. This should be noted. It is often useful to reduce the size of the redirected screen by using, for example

vncserver -query localhost -geometry 800x600

You can also use the -once option to instruct the server to run for a single session only and then exit automatically. The first time vncserver is called, you will be asked for a password. You will need this later in order to access the server. It does not have to be the user password. To change the password, delete the file

~/.vnc/passwd

You will then have to enter a new one the next time you start the server.

Establishing an SSH tunnel

On the Windows client, start an SSH connection to the server with PuTTY, i.e. start PuTTY, select host and port 22. In addition, two ports must be tunneled. This works like this:

  • Select "Connection/SSH/Tunnels" from the menu on the left.
  • Source port: 5801
  • Destination: rechner.math.tu-clausthal.de:5801
  • and click Add, then do the same with 5901.
  • <it>The last digit must correspond to the number of the X server (see above)!
  • Select "Open" and log in with ID and password.
Example of PuTTY configuration

View in the browser

Start WWW browser and enter the URL

localhost

(adjust the last digit again). A Java display of the screen redirection is running. The image content is transferred as a JPEG, so it is not particularly fast. This is sufficient for most programs within the Mathematics Institute, but you probably don't want to work with it permanently.

View with viewer

It is best to use TightVNC here. Once the SSH tunnel is established, simply start the program and enter the display number of the VNC server (see above, e.g. localhost:1). Now you can adjust the options if necessary, especially with regard to data compression. The viewer then simply asks for the VNC password stored on the server and you're ready to go.

Exit

  • client: Exit browser/viewer

  • server: Terminate vncserver with

    vncserver -kill :1
  • (not applicable with option -once)
  • client: Terminate SSH connection/PuTTY.