Puppet - Facter & Facts

Puppet supports holding multiple values as an environment variable. This feature is supported in Puppet by using facter. In Puppet, facter is a standalone tool that holds the environment level variable. In can be considered similar to env variable of Bash or Linux. Sometimes there can be an overlap between the information stored in facts and environment variable of the machine. In Puppet, the key-value pair is known as “fact”. Each resource has its own facts and in Puppet the user has the leverage to build their own custom facts.
# facter 

Facter command can be used to list all the different environment variables and its associated values. These collection of facts comes with facter out-of-the-box and are referred to as core facts. One can add custom facts to the collection.
If one wants to view only one variable. It can be done using the following command.
# facter {Variable Name}  

Example 
[root@puppetmaster ~]# facter virtual 
virtualbox 

The reason why facter is important for Puppet is that facter and facts are available throughout Puppet code as “global variable”, which means it can be used in the code at any point of time without any other reference.
[root@puppetmaster modules]# tree brcle_account 
brcle_account 
└── manifests  └── init.pp [root@puppetmaster modules]# cat brcle_account/manifests/init.pp  
class brcle_account {  
   user { 'G01063908': 
      ensure => 'present', 
      uid => '121', 
      shell => '/bin/bash', 
      home => '/home/G01063908', 
   }  
   
   file {'/tmp/userfile.txt': 
      ensure => file, 
      content => "the value for the 'OperatingSystem' fact is: $OperatingSystem \n", 
   } 
} 
[root@puppetmaster modules]# puppet agent --test 
Notice: /Stage[main]/Activemq::Service/Service[activemq]/ensure: 
ensure changed 'stopped' to 'running' 
Info: /Stage[main]/Activemq::Service/Service[activemq]: 
Unscheduling refresh on Service[activemq] 

Notice: Finished catalog run in 4.09 seconds  
[root@puppetmaster modules]# cat /tmp/testfile.txt  
the value for the 'OperatingSystem' fact is: Linux   

[root@puppetmaster modules]# facter OperatingSystem 
Linux
As we can notice in the above code snippet, we haven’t defined the OperatingSystem. We have just replaced the value with soft coded value $OperatingSystem as normal variable.
In Puppet, there are three types of fact that can be used and defined −
Core Facts
Custom Facts
External Facts
Core facts are defined at the top level and accessible to all at any point in the code.
Just before an agent requests for a catalog from the master, the agent first compiles a complete list of information available in itself in the form of a key value pair. The information on the agent is gathered by a tool called facter and each key-value pair is referred as a fact. Following is a common output of facts on an agent.
[root@puppetagent1 ~]# facter
architecture => x86_64 
augeasversion => 1.0.0 
bios_release_date => 13/09/2012 
bios_vendor => innotek GmbH 
bios_version => VirtualBox 
blockdevice_sda_model => VBOX HARDDISK 
blockdevice_sda_size => 22020587520 
blockdevice_sda_vendor => ATA 
blockdevice_sr0_model => CD-ROM 
blockdevice_sr0_size => 1073741312 
blockdevice_sr0_vendor => VBOX 
blockdevices => sda,sr0 
boardmanufacturer => Oracle Corporation 
boardproductname => VirtualBox 
boardserialnumber => 0 

domain => codingbee.dyndns.org  
facterversion => 2.1.0 
filesystems => ext4,iso9660 
fqdn => puppetagent1.codingbee.dyndns.org 
hardwareisa => x86_64 
hardwaremodel => x86_64 
hostname => puppetagent1 
id => root 
interfaces => eth0,lo 
ipaddress => 172.228.24.01 
ipaddress_eth0 => 172.228.24.01 
ipaddress_lo => 127.0.0.1 
is_virtual => true 
kernel => Linux 
kernelmajversion => 2.6 
kernelrelease => 2.6.32-431.23.3.el6.x86_64 
kernelversion => 2.6.32 
lsbdistcodename => Final 
lsbdistdescription => CentOS release 6.5 (Final) 
lsbdistid => CentOS 
lsbdistrelease => 6.5 
lsbmajdistrelease => 6 
lsbrelease => :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0noarch:graphics-4.0-amd64:
graphics-4.0-noarch:printing-4.0-amd64:printing-4.0noarch 
macaddress => 05:00:22:47:H9:77 
macaddress_eth0 => 05:00:22:47:H9:77 
manufacturer => innotek GmbH 
memoryfree => 125.86 GB 
memoryfree_mb => 805.86 
memorysize => 500 GB 
memorysize_mb => 996.14 
mtu_eth0 => 1500 
mtu_lo => 16436 
netmask => 255.255.255.0 
netmask_eth0 => 255.255.255.0  

network_lo => 127.0.0.0 
operatingsystem => CentOS 
operatingsystemmajrelease => 6 
operatingsystemrelease => 6.5 
osfamily => RedHat 
partitions => {"sda1"=>{
"uuid"=>"d74a4fa8-0883-4873-8db0-b09d91e2ee8d", "size" =>"1024000", 
"mount" => "/boot", "filesystem" => "ext4"}, "sda2"=>{"size" => "41981952", 
"filesystem" => "LVM2_member"}
} 
path => /usr/lib64/qt3.3/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin 
physicalprocessorcount => 1 
processor0 => Intel(R) Core(TM) i7 CPU         920  @ 2.67GHz 
processor1 => Intel(R) Core(TM) i7 CPU         920  @ 2.67GHz 
processor2 => Intel(R) Core(TM) i7 CPU         920  @ 2.67GHz 
processorcount => 3 
productname => VirtualBox 
ps => ps -ef 
puppetversion => 3.6.2 
rubysitedir => /usr/lib/ruby/site_ruby/1.8 
rubyversion => 1.8.7
selinux => true 
selinux_config_mode => enforcing 
selinux_config_policy => targeted 
selinux_current_mode => enforcing 
selinux_enforced => true 
selinux_policyversion => 24 
serialnumber => 0 
sshdsakey => AAAAB3NzaC1kc3MAAACBAK5fYwRM3UtOs8zBCtRTjuHLw56p94X/E0UZBZwFR3q7
WH0x5+MNsjfmdCxKvpY/WlIIUcFJzvlfjXm4qDaTYalbzSZJMT266njNbw5WwLJcJ74KdW92ds76pjgm
CsjAh+R9YnyKCEE35GsYjGH7whw0gl/rZVrjvWYKQDOmJA2dAAAAFQCoYABgjpv3EkTWgjLIMnxA0Gfud
QAAAIBM4U6/nerfn6Qvt43FC2iybvwVo8ufixJl5YSEhs92uzsW6jiw68aaZ32q095/gEqYzeF7a2knr
OpASgO9xXqStYKg8ExWQVaVGFTR1NwqhZvz0oRSbrN3h3tHgknoKETRAg/imZQ2P6tppAoQZ8wpuLrXU
CyhgJGZ04Phv8hinAAAAIBN4xaycuK0mdH/YdcgcLiSn8cjgtiETVzDYa+jF 
swapfree => 3.55 GB 
swapfree_mb => 2015.99 
swapsize => 3.55 GB 
swapsize_mb => 2015.99 
timezone => GMT 
type => Other 
uniqueid => a8c0af01 
uptime => 45:012 hours 
uptime_days => 0 
uptime_hours => 6 
uptime_seconds => 21865 
uuid => BD8B9D85-1BFD-4015-A633-BF71D9A6A741 
virtual => virtualbox 

In the above code, we can see some of the data overlap with few of the information available in bash “env” variable. Puppet directly does not use the data, instead it makes use of facter data, Facter data is treated as global variable.
The facts are then available as top level variable and the Puppet master can use them to compile the Puppet catalog for the requesting agent. Facters are called in manifest as normal variable with $ prefix.
if ($OperatingSystem == "Linux") { 
   $message = "This machine OS is of the type $OperatingSystem \n" 
} else { 
   $message = "This machine is unknown \n" 
} 

file { "/tmp/machineOperatingSystem.txt": 
   ensure => file, 
   content => "$message" 
}
The above manifest file only bothers about a single file called machineOperatingSystem.txt, where the content of this file is deducted by the fact called OperatingSystem.
[root@puppetagent1 /]# facter OperatingSystem 
Linux  

[root@puppetagent1 /]# puppet apply /tmp/ostype.pp 
Notice: Compiled catalog for puppetagent1.codingbee.dyndns.org 
in environment production in 0.07 seconds 
Notice: /Stage[main]/Main/File[/tmp/machineOperatingSystem.txt]/ensure: 
defined content as '{md5}f59dc5797d5402b1122c28c6da54d073' 
Notice: Finished catalog run in 0.04 seconds  

[root@puppetagent1 /]# cat /tmp/machinetype.txt 
This machine OS is of the type Linux
All the above facts that we have seen are the core facts of the machine. One can add this custom facts to the node in the following ways −
Using the “export FACTER ... Syntax”
Using the $LOAD_PATH settings
FACTERLIB
Pluginsync
One can manually add the facts using the export FACTER_{fact’s name} syntax.
[root@puppetagent1 facter]# export FACTER_tallest_mountain="Everest" 
[root@puppetagent1 facter]# facter tallest_mountain Everest

In Ruby, $LOAD_PATH is equivalent to Bash special parameter. Although it is similar to bash $PATH variable, in real facts $LOAD_PATH is not an environment variable, instead it is a pre-defined variable.
$LOAD_PATH has a synonym “$:”. This variable is an array to search and load the values.
[root@puppetagent1 ~]# ruby -e 'puts $LOAD_PATH'            
# note you have to use single quotes.  
/usr/lib/ruby/site_ruby/1.6 
/usr/lib64/ruby/site_ruby/1.6 
/usr/lib64/ruby/site_ruby/1.6/x86_64-linux 
/usr/lib/ruby/site_ruby 
/usr/lib64/ruby/site_ruby 
/usr/lib64/site_ruby/1.6 
/usr/lib64/site_ruby/1.6/x86_64-linux 
/usr/lib64/site_ruby 
/usr/lib/ruby/1.6 
/usr/lib64/ruby/1.6 
/usr/lib64/ruby/1.6/x86_64-linux 

Let’s take an example of creating a directory facter and adding a .pp file and appending a content to it.
[root@puppetagent1 ~]# cd /usr/lib/ruby/site_ruby/ 
[root@puppetagent1 site_ruby]# mkdir facter 
[root@puppetagent1 site_ruby]# cd facter/ 
[root@puppetagent1 facter]# ls 
[root@puppetagent1 facter]# touch newadded_facts.rb 

Add the following content to the custom_facts.rb file.
[root@puppetagent1 facter]# cat newadded_facts.rb 
Facter.add('tallest_mountain') do 
   setcode "echo Everest" 
end 

Facter works in the method of scanning through all the folder listed in $LOAD_PATH, and looks for a director called facter. Once it finds that particular folder, it will load them anywhere in the folder structure. If it finds this folder then it looks for any Ruby file in that facter folder and loads all the defined facts about any particular configuration in the memory.
In Puppet, FACTERLIB works very much similar to $LOAD_PATH but with only one key difference that, it is a OS level environment parameter rather than a Ruby special variable. By default, the environment variable may not be set.
[root@puppetagent1 facter]# env | grep "FACTERLIB" 
[root@puppetagent1 facter]# 

To test FACTERLIB, we need to perform the following steps.
Create a folder called test_facts in the following structure.
[root@puppetagent1 tmp]# tree /tmp/test_facts/ 
/tmp/some_facts/ 
├── vipin 
│   └── longest_river.rb 
└── testing 
   └── longest_wall.rb 

Add the following contents to the .rb files.
[root@puppetagent1 vipin]# cat longest_river.rb 
Facter.add('longest_river') do 
   setcode "echo Nile" 
end 

[root@puppetagent1 testing]# cat longest_wall.rb 
Facter.add('longest_wall') do 
   setcode "echo 'China Wall'" 
end 
Use the export statement.
[root@puppetagent1 /]# export 
FACTERLIB = "/tmp/some_facts/river:/tmp/some_facts/wall" 
[root@puppetagent1 /]# env | grep "FACTERLIB" 
FACTERLIB = /tmp/some_facts/river:/tmp/some_facts/wall 

Test the new facter.
[root@puppetagent1 /]# facter longest_river 
Nile 
[root@puppetagent1 /]# facter longest_wall 
China Wall 

External facts are very useful when the user wishes to apply some new facts created at the provisioning time. External facts are one of the key ways of applying metadata to a VM at its provisioning stage (e.g. using vSphere, OpenStack, AWS, etc.)
All the metadata and its details created can be used by Puppet to determine what details should be present in the catalog, which is going to be applied.
On the agent machine, we need to create a directory as mentioned below.
$ mkdir -p /etc/facter/facts.d

Create a Shell script in the directory with the following content.
$ ls -l /etc/facter/facts.d 
total 4 
-rwxrwxrwx. 1 root root 65 Sep 18 13:11 external-factstest.sh 
$ cat /etc/facter/facts.d/external-factstest.sh 
#!/bin/bash 
echo "hostgroup = dev" 
echo "environment = development"

Change the permission of the script file.
$ chmod u+x /etc/facter/facts.d/external-facts.sh

Once done, we can now see the variable present with the key/value pair.
$ facter hostgroup 
dev 
$ facter environment 
development 

One can write custom facts in Puppet. As a reference, use the following link from the Puppet site.
https://docs.puppet.com/facter/latest/fact_overview.html#writing-structured-facts
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