External facts

An example external fact written in Python:

#!/usr/bin/env python
data = {"key1" : "value1", "key2" : "value2" }

for k in data:
    print "%s=%s" % (k,data[k])

You must ensure that the script has its execute bit set:

chmod +x /etc/facter/facts.d/my_fact_script.py

For Facter to parse the output, the script must return key-value pairs on STDOUT in the format:

key1=value1
key2=value2
key3=value3

Using this format, a single script can return multiple facts.

Executable facts on Windows work by dropping an executable file into the external fact path. Unlike with Unix, the external facts interface expects Windows scripts to end with a known extension. Line endings can be either LF or CRLF. The following extensions are supported:

• .com and .exe: binary executables

• .bat and .cmd: batch scripts

• .ps1: PowerShell scripts

As with Unix facts, each script must return key-value pairs on STDOUT in the format:

key1=value1
key2=value2
key3=value3

Using this format, a single script can return multiple facts in one return.

Here is a sample batch script which outputs facts using the required format:

@echo off
echo key1=val1
echo key2=val2
echo key3=val3
REM Invalid - echo 'key4=val4'
REM Invalid - echo "key5=val5"

Here is a sample PowerShell script which outputs facts using the required format:

Write-Host "key1=val1"
Write-Host 'key2=val2'
Write-Host key3=val3

Save and execute this PowerShell script on the command line.

In a module (recommended):

<MODULEPATH>/<MODULE>/facts.d/

On Unix, Linux, or Mac OS X, there are three directories:

/opt/puppetlabs/facter/facts.d/
/etc/puppetlabs/facter/facts.d/
/etc/facter/facts.d/

On Windows:

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

When running as a non-root or non-Administrator user:

<HOME DIRECTORY>/.facter/facts.d/

Structured data files must use one of the supported data types and must have the correct file extension. Facter supports the following extensions and data types:

• .yaml: YAML data, in the following format:

  ---
  key1: val1
  key2: val2
  key3: val3

• .json: JSON data, in the following format:

  { "key1": "val1", "key2": "val2", "key3": "val3" }

• .txt: Key-value pairs, of the String data type, in the following format:

  key1=value1
  key2=value2
  key3=value3

As with executable facts, structured data files can set multiple facts at one time.

{
  "datacenter":
  {
    "location": "bfs",
    "workload": "Web Development Pipeline",
    "contact": "Blackbird"
  },
  "provision":
  {
    "birth": "2017-01-01 14:23:34",
    "user": "alex"
  }
}

If your external fact is not appearing in Facter’s output, running Facter in debug mode can reveal why and tell you which file is causing the problem:

# puppet facts --debug

One possible cause is a fact that returns invalid characters. For example if you used a hyphen instead of an equals sign in your script test.sh:

#!/bin/bash

echo "key1-value1"

Running puppet facts --debug yields the following message:

...
Debug: Facter: resolving facts from executable file "/tmp/test.sh".
Debug: Facter: executing command: /tmp/test.sh
Debug: Facter: key1-value1
Debug: Facter: ignoring line in output: key1-value1
Debug: Facter: process exited with status code 0.
Debug: Facter: completed resolving facts from executable file "/tmp/test.sh".
...

While external facts provide a mostly-equal way to create variables for Puppet, they have a few drawbacks:

• An external fact cannot internally reference another fact. However, due to parse order, you can reference an external fact from a Ruby fact.

• External executable facts are forked instead of executed within the same process.