Specify the JSON config to use for the selenium node. This config will be written to disk and the file path will be passed to the grid with the -nodeConfig parameter. See https://code.google.com/p/selenium/wiki/Grid2 and https://code.google.com/p/selenium/source/browse/java/server/src/org/openqa/grid/common/defaults/DefaultNode.json on how to specify a JSON input.