Virtual Frame Buffer for Batch Mode
Often there is a need to run a program with a graphical interface in batch mode. This can be either due to extended run-time or the desire to run many instances of the process at once. In either case the lack of a display can prevent the program from running.
A solution has been developed to create a virtual display that only lives in memory. This allows the program to happily launch its graphical interface while in batch mode.
Note
It is common for R to require a display session to save certain types of figures.
You may see a warning like "unable to start device PNG" or "unable to open connection to X11 display".
xvfb can help avoid these issues.
This tool is called the X Virtual Frame Buffer or xvfb.
It can act as a wrapper to your script which creates a virtual display session.
For example, to run an R script (e.g. make_jpeg.R) which needs a display session in order to save a JPEG file:
xvfb-run Rscript make_jpeg.R
For more details and other examples see the xvfb-run man page by running man xvfb-run on any compute node.