You can prove anything with facts!

gem install facter -v 3.9.6.cfacter.20180412


Native Facter

An implementation of facter functionality in C++11, providing:

  • a shared library which gather facts about the system
  • an executable for standalone command line usage
  • a ruby file to enable require 'facter'.

Please see our extensibility document to learn more about extending native facter using custom and external facts.

Build Requirements

  • GCC 4.8+ or Clang 5.0+ (OSX)
  • CMake >= 3.2.2
  • Boost C++ Libraries >= 1.54
  • yaml-cpp >= 0.5.1
  • leatherman >= 1.0.0
  • cpp-hocon >= 0.1.0

Optional Build Libraries

  • OpenSSL - enables SSH fingerprinting facts.
  • libblkid (Linux only) - enables the partitions fact.
  • libcurl >= 7.18.0 - enables facts that perform HTTP requests.

Initial Setup

Note: Testing custom facts requires Ruby 1.9+ with libruby built as a dynamic library; that often implies development builds of Ruby.

Setup on Fedora 23

The following will install all required tools and libraries:

dnf install boost-devel openssl-devel yaml-cpp-devel libblkid-devel libcurl-devel gcc-c++ make wget tar cmake

Setup on Mac OSX El Capitan (homebrew)

This assumes Clang is installed and the system OpenSSL libraries will be used.

The following will install all required libraries:

brew install cmake boost yaml-cpp

Setup on Ubuntu 15.10 (Trusty)

The following will install most required tools and libraries:

apt-get install build-essential libboost-all-dev libssl-dev libyaml-cpp-dev libblkid-dev libcurl4-openssl-dev wget tar cmake

Setup on FreeBSD 10

The following will install most required tools and libraries:

pkg install git ruby21 cmake boost-all yaml-cpp gcc49

Setup on Windows

MinGW-w64 is used for full C++11 support, and Chocolatey can be used to install. You should have at least 2GB of memory for compilation.

  • install CMake

  • install MinGW-w64

      choco install mingw --params "/threads:win32"

For the remaining tasks, build commands can be executed in the shell from Start > MinGW-w64 project > Run Terminal

  • select an install location for dependencies, such as C:\tools or cmake\release\ext; we'll refer to it as $install

  • build Boost

      .\bootstrap mingw
      .\b2 toolset=gcc --build-type=minimal install --prefix=$install --with-program_options --with-system --with-filesystem --with-date_time --with-thread --with-regex --with-log --with-locale --with-chrono boost.locale.iconv=off
  • build yaml-cpp

      cmake -G "MinGW Makefiles" -DCMAKE_PREFIX_PATH=$install -DCMAKE_INSTALL_PREFIX=$install .
      mingw32-make install
  • build libcurl

      mingw32-make mingw32
      cp -r include\curl $install\include
      cp -r lib\libcurl.a $install\lib

In Powershell:

choco install cmake 7zip.commandline -y
$env:PATH = "C:\Program Files\CMake\bin;$env:PATH"
choco install mingw --params "/threads:win32" -y
$env:PATH = "C:\tools\mingw64\bin;$env:PATH"
$install = "C:\tools"

(New-Object Net.WebClient).DownloadFile("", "$pwd/boost_1_54_0.7z")
7za x boost_1_54_0.7z
pushd boost_1_54_0
.\bootstrap mingw
.\b2 toolset=gcc --build-type=minimal install --prefix=$install --with-program_options --with-system --with-filesystem --with-date_time --with-thread --with-regex --with-log --with-locale --with-chrono boost.locale.iconv=off

(New-Object Net.WebClient).DownloadFile("", "$pwd/yaml-cpp-0.5.3.tar.gz")
7za x yaml-cpp-0.5.3.tar.gz
7za x yaml-cpp-0.5.3.tar
pushd yaml-cpp-yaml-cpp-0.5.3
cmake -G "MinGW Makefiles" -DCMAKE_PREFIX_PATH="$install" -DCMAKE_INSTALL_PREFIX="$install" .
mingw32-make install

(New-Object Net.WebClient).DownloadFile("", "$pwd/")
7za x
pushd curl-7.42.1
mingw32-make mingw32
cp -r include\curl $install\include
cp -r lib\libcurl.a $install\lib

Note that OpenSSL isn't needed on Windows.

Setup on OpenBSD 6.0

The following will install all required tools and libraries:

pkg_add boost cmake curl g++ ruby yaml-cpp

Optionally leatherman can be installed from packages too if not built locally.

Build and install Leatherman and cpp-hocon

Leatherman and cpp-hocon are built similar to the Pre-Build instructions below. If building on Windows, install to the same $install location used for other dependencies.


All of the following examples start by assuming the current directory is the root of the repo.

On Windows, add -G "MinGW Makefiles" -DCMAKE_PREFIX_PATH=\<binary install path\> -DBOOST_STATIC=ON to the cmake invocation.

Before building facter, use cmake to generate build files:

$ mkdir release
$ cd release
$ cmake ..

To generate build files with debug information:

$ mkdir debug
$ cd debug
$ cmake -DCMAKE_BUILD_TYPE=Debug ..


To build facter, use 'make':

$ cd release
$ make

To build facter with debug information:

$ cd debug
$ make


You can run facter from where it was built:

$ release/bin/facter

For a debug build:

$ debug/bin/facter


If a ruby was found during configuration, execute the following command before running tests:

$ bundle install --gemfile lib/Gemfile

You can run facter tests using the test target:

$ cd release
$ make test

For a debug build:

$ cd debug
$ make test

For verbose test output, run ctest instead of using the test target:

$ cd release
$ ctest -V


You can install facter into your system:

$ cd release
$ make && sudo make install

By default, facter will install files into /usr/local/bin, /usr/local/lib, and /usr/local/include. If the project is configured with Ruby in the PATH, facter.rb will be installed to that Ruby's vendor dir. The install location for facter.rb can be overridden using by setting RUBY_LIB_INSTALL.

To install to a different location, set the install prefix:

$ cd release
$ make clean install

This would install facter into ~/bin, ~/lib, and ~/include.

Ruby Usage

Using the Ruby API requires that facter.rb is installed into the Ruby load path, as done in the previous install steps.

    require 'facter'

    # Use the Facter API...
    puts "kernel: #{Facter.value(:kernel)}"


Facter can be configured via a HOCON config file of the following format:

global : {
    external-dir     : [ "path1", "path2" ],
    custom-dir       : [ "custom/path" ],
    no-exernal-facts : false,
    no-custom-facts  : false,
    no-ruby          : false
cli : {
    debug     : false,
    trace     : true,
    verbose   : false,
    log-level : "warn"
facts : {
    blocklist : [ "file system", "EC2" ]
    ttls : [
        { "timezone" : 30 days },

All options are respected when running Facter standalone, while calling Facter from Ruby will only load external-dir, custom-dir, and the fact-specific configuration.

The file will be loaded by default from /etc/puppetlabs/facter/facter.conf on Unix and C:\ProgramData\PuppetLabs\facter\etc\facter.conf on Windows. A different location can be specified using the --config command line option.

Elements in the blocklist are fact groupings which will not be resolved when Facter runs. Use the --list-block-group command line option to see valid blockable groups.

Elements in the ttls section are key-value pairs of fact groupings that will be cached with the duration for which to cache them. Cached facts are stored as JSON in /opt/puppetlabs/facter/cache/cached_facts on Unix and C:\ProgramData\PuppetLabs\facter\cache\cached_facts on Windows. Use the --list-cache-groups command line option to see valid cacheable groups.


Run the following command to remove files that were previously installed:

$ sudo xargs rm < release/install_manifest.txt


To generate API documentation, install doxygen 1.8.7 or later.

$ cd lib
$ doxygen

To view the documentation, open lib/html/index.html in a web browser.


If when running the tests you encounter this error message:

"could not locate a ruby library"

You may need to use a different shared ruby library in Leatherman. To do this, run this command, where the location below is the default for a puppet agent installation:

$ export LEATHERMAN_RUBY=/opt/puppetlabs/puppet/lib/libruby.dylib