When you define custom facts within your modules (in the lib/facter directory), they are automatically transferred to your node via the pluginsync method. The issue here is that the facts are synced to the same directory. So, if you created two facts with the same filename, then it can be difficult to determine which fact will be synced down to your node.

Facter is run at the beginning of a Puppet agent run. The results of Facter are used to compile the catalog. If any of your facts take longer than the configured timeout (config_timeout in the [agent] section of puppet.conf) in Puppet, then the agent run will fail. Instead of increasing this timeout, when designing your custom facts keep them simple enough so that they will take no longer than a few seconds to run.

You can debug Facter from the command line using the -d switch. To load custom facts that are synced from Puppet, add the -p option as well. If you are having trouble with the output of your fact, then you can also...