Puppet, my favourite system administration tool, gathers facts about its managed hosts which can be used in administering these hosts.
These default facts are collected by Facter, one of Puppet’s dependencies. One can use these facts by querying using ‘facter’ on a managed host and in Puppet recipes, i.e. a description of how you want your hosts to be configured. A rather big set of facts are supported out of the box. Adding facts, however, can help you in making your recipes more clever.
That’s what I’ve been doing over the last couple of days. This page, “Plugins in Modules“, explains rather well how to add your custom facts. What it fails to tell you is that facts added through this mechanism are only available to Puppet and not to Facter.
So reading this blog post can save you hours trying to figure out why you custom facts don’t show up in the output of facter, because they never will. Executing a mail statement in which you mail the output of a fact, will show you the contents of your facts, however… 
