The Puppet agent
Managed nodes run the Puppet agent application, usually as a background service. The primary server and any compilers also run a Puppet agent.
Periodically, the agent sends facts to a primary server and requests a catalog. The primary server compiles the catalog using several sources of information, and returns the catalog to the agent.
After it receives a catalog, the agent applies it by checking each resource the catalog describes. If it finds any resources that are not in their desired state, it makes the changes necessary to correct them. (Or, in no-op mode, it reports on what changes would have been made.)
After applying the catalog, the agent submits a report to its primary server. Reports from all the agents are stored in PuppetDB and can be accessed in the console.
Puppet agent runs on *nix and Windows systems.
Facter
Facter is the cross-platform system profiling library in Puppet. It discovers and reports per-node facts, which are available in your Puppet manifests as variables.
Before requesting a catalog, the agent uses Facter to collect system information about the machine it’s running on.
For example, the fact os returns information about the host operating
system, and networking returns the
networking information for the system. Each fact has various elements to further refine
the information being gathered. In the networking fact, networking.hostname provides the hostname of the system.
Facter ships with a built-in list of core facts, but you can build your own custom facts if necessary.
You can also use facts to determine the operational state of your nodes and even to group and classify them in the NC.
