The Ohai plugin is used to detect information about the client operating system. The data is reported back to the server using JSON.
If you have python 2.6 or later installed, you can continue on to Setup. Otherwise, you will need to install the python-simplejson module found packaged in most distributions.
To enable the Ohai plugin, you need to first create an Ohai directory in your Bcfg2 repository (e.g. /var/lib/bcfg2/Ohai). You then need to add Ohai to the plugins line in bcfg2.conf. Once this is done, restart the server and start a client run. You will have the JSON output from the client in the Ohai directory you created previously.