VNC (Virtual Network Computing) is a graphical desktop sharing system that allows users to remotely work on another computer. It works by transmitting the keyboard and mouse events from your local machine to the remote machine. VNC is now available on all of the SCC login nodes; but requires setup before using. Using VNC on the Shared Computing Cluster (SCC) presents two major benefits:
  1. It provides high graphics compression, so you can use GUI-based and graphics applications at a speed comparable to if the application was running on your local machine.
  2. VNC session is persistent, so you can suspend your session, disconnect your computer and resume your session at a later time.

VNC Server Setup

Table of Contents

  1. VNC Server setup
  2. Configure SSH tunnel
  3. Connect with VNC Client – PC
  4. Connect with VNC Client – Mac
  5. Terminating VNC server
  6. Stop SSH tunneling
  7. Running Interactive Jobs on SCC cluster during VNC session
  8. Frequently Asked Questions

VNC Server setup

Login to the SCC cluster using any login node. The first time you use vncserver, you have to establish your VNC password. This VNC password must be different from your Kerberos password and, if you have one, your local SCC Linux password. To setup VNC password, execute the following command:
scc1% vncpasswd
To start VNC server, run the following script in your SCC Linux terminal window:
scc1% vncstart
If vncserver started successfully you will see an output similar to the following:
Launching VNC server ...


     *** Your VNC server is now running! ***

         VNC desktop number: 6

         VNC Port number: 5906

To connect via VNC client:
1. On your local machine execute the following command:

    ssh koleinik@scc1.bu.edu -L XXXX:localhost:5906

	    where XXXX - some number greater than 1023.

2. Start your local VNC Client application and enter the following address 
in VNC server field:

This output will provide you with a VNC desktop and port information. It will also give you the detailed information about configuring SSH tunneling and setting up the VNC client.

Configure SSH tunnel

Linux and Mac users can execute the ssh command, given in step <b1. of the vncstart script output. This should be entered in your local machine’s terminal window, e.g.
> ssh koleinik@scc1.bu.edu -L 7070:localhost:5906
You will be asked to enter your Kerberos/SCC password. If the number XXXX you chose for SSH tunneling is not available, you might get an error message that includes the text “cannot listen to port:” and “Could not request local forwarding.“. In this situation, try another port number, such as one number higher. It is important that you keep this connection running while using VNC. Windows users can execute the same command in their MobaXterm or Cygwin local terminal window or follow these steps to set up tunneling using putty.

Connect with VNC Client – PC

If you do not have the VNC viewer built into your system, download it from www.realvnc.com. When you install it, select only the VNC Viewer (you do not need to install VNC server on your local machine). Start the VNC Viewer and when a dialog window appears, enter:
VNC server: localhost:XXXX
where XXXX is the number you selected while configuring SSH tunneling (7070 in the example above). You will be prompted to enter your password. Use your VNC (not Kerberos) password.

Connect with VNC Client – MAC

Recent versions of Mac OSX have a VNC client built into the operating system. To connect on a Mac, click on the desktop then press the key combo ⌘-K. In the Connect to Server window that opens, enter the following into the Server Address box, using the port number selected earlier in place of the XXXX:
You will be prompted to enter your password. Use your VNC (not Kerberos) password.

Terminating VNC server

When you quit the VNC viewer, the remote VNC server stays running. You can reconnect to the same session at a later time. Please terminate your VNC server when you no longer need it.
Use the Desktop number you were given in the script output to terminate the server, using vncserver -kill :desktop_number command, e.g.:
% vncserver -kill :6

Stop SSH tunneling

To stop the tunnel, log out of the ssh session you started on your local machine.

Running Interactive Jobs on SCC cluster during VNC session

All SCC usage policies remain the same during your work using a VNC connection. Any job that requires more than 15 minutes of CPU time should be executed on one of the compute nodes. Use the qsh or qrsh command to start an interactive batch job. Please refer to the SCC Running Jobs page for more information about how to start an interactive batch job.