In the examples/ directory of the distribution you will find some pre-generated pbsnodes xml files and an example configuration file.
The first example works for the RRZN cluster system (http://www.rrzn.uni-hannover.de/computeserver.html). Change into the examples/ directory and run the following command:
$ cluster_status -x pbsnodes_rrzn.xml -n nodes.rrzn -c rrznviz.conf -i