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Howto: Use VNC for remote graphical access to the ifarm

WORK IN PROGRESS, DO NOT USE HOWTO YET!

Most of the time, a simple ssh session will be sufficient to perform remote work on the JLab interactive farm. In principle, ssh with graphics forwarding (called X-forwarding) could be used if you need to access the graphical environment, for example to interact with figures. However, due to the way X-forwarding operates, this may be unworkably slow. This is where VNC comes in.

The VNC protocol, designed for graphical desktop-sharing, will give you direct access to the graphical desktop environment of a remote computer system, such as the ifarm. This is the prefered mode of operation in those (rare) cases where you need to interact with graphical applications (for example if you want to look at a histogram you just generated).

The VNC protocol uses a Client-Server architecture. You will have to run a VNC server on the system you want to access (jlabl5 in this case), and use a VNC client on your local machine to connect to the session.

Note that the VNC protocol itself is inherently insecure. To mitigate this, you will have to establish an SSH tunnel from you local machine to the JLab ifarm to connect to the VNC server.

Some of the following tutorial exercises could be performed either using ssh tunneling, or a VNC session.

Step 0: Login to the node of choice (jlabl5)

Start by logging into jlabl5 (replace USER with your JLab user name).

ssh USER@login.jlab.org 
ssh jlabl5

Step 1: Configure and launch the VNC server

On the JLab farm