external_facts.md

Puppet external facts

There are 3 ways to add our own facts in Puppet:

• Writing our custom facts, in Ruby language and adding them to the lib/facter directory of a module. Details here

• Adding trusted facts in csr_attributes.yaml as described in this document

• Adding external facts, written in plain text or as executables in any language. Details below:

External facts are placed in these directories:

On Linux/*nix:
/opt/puppetlabs/facter/facts.d/
/etc/puppetlabs/facter/facts.d/
/etc/facter/facts.d/

On Windows:
C:\ProgramData\PuppetLabs\facter\facts.d\

They are simple files that can have different formats:

• Simple *.txt files. Facts names and their values are in .ini file format:

    role=webserver
    env=prod
    zone=berlin
  

• Yaml files, with .yaml extension:

    ---
    role: webserver
    env: prod
    zone: berlin
  

• Json files, with .json extension:

    {
      "role": "webserver",
      "env": "prod",
      "zone": "berlin",
    }
  

• Any command in any language. On Linux/*nix the file, with whatever extension, just has to be executable. On Windows it must have .com, .exe, .bat, .cmd, .ps1 extension. The command should just output the fact name(s) and its/their values:

    #!/bin/bash
    echo "role=webserver"
    echo "env=prod"
    echo "zone=berlin"
  

The files we create on client in the facts.d directory can provide one or more facts values, and they can have any name. Typically, for data files that provide just one fact, the file name is the name of the fact:

cat /etc/puppetlabs/facter/facts.d/role.txt
role=webserver

External facts can be deployed during provisioning of the server or can be placed in the facts.d directory of a module (they are pluginsynced automatically to the client at the beginning of each Puppet run).

External facts are a very easy way to set custom facts on nodes, just consider the following points:

• They can be potentially changed on the client just by editing the relevant fact. We may prefer to use trusted facts when we want their values to be immutable.

• If we use the pluginsync functionality to distribute them note that they are copied as is, from Puppet Server to clients, so we don't have a way to distribute different facts to different clients. For this reason we'll probably find ourselves adding facts to the clients that just contain data (.txt, .yaml, .json) in some alternative way (typically during the node's provisioning) and use pluginsync only for the ones that compute the result in some way (as executables ones do).