Developing Modules in Puppet

Modules 📌

Before moving on to the discussion of developing modules in puppet, let us have a basic overview of the modules. 

About Modules

The puppet code is kept in the modules. There is a specific module for specific tasks. The developer can reuse and share the modules, also. The module comprises functions, classes, different tasks, and plans. The modules can easily be installed from puppet forge. It contains a library of modules.

There are numerous classes and functions defined in the module. The puppet finds the desired data using the directory system of the modules.

One important thing to note is that the names of the modules cannot contain the namespace separator(::).

Managing Modules

You can use the puppet module command to upgrade or install the puppet forge modules from the command line.

Setting Up the Puppet Module Using a Proxy

You first need to set the IP address of the proxy to set up the puppet modules behind it. To do this you can run the commands mentioned below.

export http_proxy=http://<PROXY IP>:<PROXY PORT>
export https_proxy=http://<PROXY IP>:<PROXY PORT

Installing Modules From Command Line

To use a module you first have to install it and all its dependencies. To do this you can use the puppet module install command.

Installing Modules From Puppet Forge

To install a module from the puppet forge, run the puppet module install command. You also have to mention the name of the module along. The command is given below.

puppet module install puppetlabs-<nameofmodule>

Upgrading Modules💻

You can simply use the puppet module upgrade to upgrade the modules. You can upgrade the module with a specific version. The command for this is given below.

puppet module upgrade puppetlabs-<modulename> --version 2.3.1

Uninstalling Modules🎯

You can simply uninstall the modules using the puppet module uninstall command. The proper command to remove a module is given below.

puppet module uninstall puppetlabs-apache

The command to uninstall the dependencies forcibly is as follows.

puppet module uninstall --force

Writing Modules📍

In this section we will define the basic design of a module. A great module contains small classes. These classes are like functions. This is used to perform tasks. Some of the main classes in a module are as follows.

⭕<module> class

This has the name of the module.

⭕Install class

It has information about the resources managing the installation of software.

⭕Service class

It has information about resources and the running state of the software.

Puppet Development Kit💻

This part of the blog will form the basis for developing modules in puppet. Puppet development kit is the framework that lets you write your puppet module. You can also test your module using puppet development kit. You can also modify the current modules according to the puppet development kit.

The official site of puppet development kit looks like this.

Steps To Follow While Developing Modules In Puppet📃

The steps involved in working with the puppet development kit are as follows.

📌Create a module.

📌Test and validate your module.

📌Make sure that the dependencies required are already present.

📌Start with writing the classes.

📌 Every time you add a new feature, ensure that the module functions appropriately.

Puppet Development Kit Package✅

The tools that are included in the puppet development kit package are shown in a tabular manner below.

Tool	Definition
pdk	It is used to create and test modules.
puppet-syntax	It is used to validate the syntax of puppet.
puppet-lint	Validates the code of puppet by comparing it with the standard style of puppet.
metadata-json-lint	Checks the metadata.json files by comparing it with the standard style of puppet.
rspec-puppet-facts	Using this tool, you can also add rspec-puppet tests for certain systems.

The table lists out the tools and their definition.

Puppet and VS Code💻

Interestingly, the puppet has an extension in the VSCode( Visual Studio Code). This extension is developed exclusively for making the puppet code writing more quickly. It works with all operating systems like windows, linux, etc.

Starting with VSCode Extension🎯

📌Download the puppet development kit on your system.

📌Install the VS Code extension for puppet. You can refer to the link given below.

Puppet - Visual Studio Marketplace

📌Create a puppet file. The file must have .pp extension.

📌Search for the puppet-vscode extension from the extension option. Click on install. The extension will be installed in your system.

DSC Resources Powershell💻

DSC stands for Desired State Configuration. DSC is useful in managing configuration as code. The DSC resources can be small or large. You can directly install the DSC resources using puppet forge. You have to then deploy it to the code base.

Let us understand the DSC resources through an example.

If you deploy the xinternetexplorerhomepage, you have to declare the resources like mentioned below.

dsc_xinternetexplorerhomepage { 'homepage':
  dsc_ensure    => 'Present',
  dsc_startpage => 'https://puppet.com',
}

The DSC modules are not like normal modules. They have different policies.The policies are mentioned below.

📌There is a translation layer between DSC and puppet.

📌Puppet does not have a bug-supporting feature.

📌Puppet supports private modules.

Conversion of Private DSC Resources To Puppet Module🎯

A private DSC resource can be converted to a puppet module. Powershell gallery syncs the private DSC resources. The steps for conversion are given below.

📌Install the Puppet.dsc module using the command given below.

PS C:\Users\Administrator> Install-Module -Name Puppet.Dsc

📌Build the puppet module using a private PSRepository feed. The command for this is given below.

PS> New-PuppetDscModule -PowerShellModuleName YourPowerShellModule 
-PowerShellModuleVersion 2.2.3 -Repository YourRepository

Distribution of Arbitrary DSC Resources✅

Use the puppetlabs-dsc_lite module. This lets you manage your target nodes with arbitrary DSC resources. The following command lets you identify the parameters available.

PS> Get-DscResource WindowsFeature | Select-Object -ExpandProperty Properties

The puppetlabs-dsc_lite module lets you specify a version of the DSC resource to use for each resource declaration. An example where you can specify a version of DSC resource is as follows.

dsc {'iis_server':
  resource_name => 'xyz',
  module        => {
    name    => 'PSDesiredStateConfiguration',
    version => '1.1'
  },
  properties => {
    ensure => 'present',
    name   => 'xyz',
  }
}

Upgradation of Puppet DSC Modules🎯

You can upgrade the puppet DSC modules too. You can use the puppetlabs-dsc module the same. The steps for the upgradation are given below.

📌Remove the puppetlabs-dsc module from the puppetfile.

📌You should have the declarations that you want to keep. Set these declarations in place of the puppetlabs-dsc module.

📌The list of resources is given below. Choose the ones you want and add them to the puppetfile.

mod 'dsc-xdefender', '0.2.0-0-0'
mod 'dsc-xdhcpserver', '2.0.0-0-0'
mod 'dsc-xdisk', '1.0.0-0-0'
mod 'dsc-xdismfeature', '1.3.0-0-0'
mod 'dsc-xdnsserver', '1.11.0-0-0'
mod 'dsc-xexchange', '1.27.0-0-0'
mod 'dsc-xfailovercluster', '1.12.0-0-0'
mod 'ddsc-xhyper_v', '3.16.0-0-0'
mod 'dsc-xinternetexplorerhomepage', '1.0.0-0-0'
mod 'dsc-xjea', '0.2.16-6-0'
mod 'dsc-xmysql', '2.1.0-0-0'
mod 'dsc-xpendingreboot', '0.4.0-0-0'
mod 'dsc-xphp', '1.2.0-0-0'
mod 'dsc-xpowershellexecutionpolicy', '3.1.0-0-0'
mod 'dsc-xpsdesiredstateconfiguration', '8.5.0-0-0'
mod 'dsc-xremotedesktopadmin', '1.1.0-0-0'
mod 'dsc-xremotedesktopsessionhost', '1.8.0-0-0'
mod 'dsc-xrobocopy', '2.0.0-0-0'
mod 'dsc-xscdpm', '1.2.0-0-0'
mod 'dsc-xscom', '1.3.3-0-0'
mod 'dsc-xscsma', '2.0.0-0-0'
mod 'dsc-xscspf', '1.3.1-0-0'
mod 'dsc-xscsr', '1.3.0-0-0'
mod 'dsc-xscvmm', '1.2.4-0-0'
mod 'dsc-xsmbshare', '2.1.0-0-0'
mod 'dsc-xsqlps', '1.4.0-0-0'
mod 'dsc-xtimezone', '1.8.0-0-0'
mod 'dsc-xwebadministration', '2.5.0-0-0'
mod 'dsc-xwebdeploy', '1.2.0-0-0'
mod 'dsc-xwindowseventforwarding', '1.0.0-0-0'
mod 'dsc-xwindowsrestore', '1.0.0-0-0'
mod 'dsc-xwindowsupdate', '2.7.0-0`0'
mod 'dsc-xwineventlog', '1.2.0-0-0'
mod 'dsc-xwordpress', '1.1.0-0-0'

DSC Resources and Troubleshooting🎯

Validation does not happen in some of the DSC resources on their own. One example where troubleshooting might be useful is as follows. There could be a scenario where a resource accepts an integer value but retrieves the value as a string. One way of the troubleshooting here can be instructing the resource to perform validation at the resource level.
We hope you have understood the concept of developing modules in puppet🎯.

Frequently Asked Questions

What is the use of puppet forge?

The puppet forge contains over 6000 modules in a library that can be used.

What language is Puppet built on?

Puppet is built using Ruby domain-specific language.

Is puppet an open-source tool?

Puppet is an open-source tool. Puppet is also available in the enterprise version.

What is the meaning of classes in modules in puppet?

The classes in modules of puppet are basically the codes that are used to be reused further in the code.

How can I see the installed modules in puppet?

You can view all installed modules and their directories using the Puppet Module list command.

Conclusion

This blog discussed the concept of developing modules in puppet. We first started with discussing about puppet. We then proceeded to learning about modules in puppet followed by a discussion on puppet development kit. The blog further explained about puppet vs code extension in detail and DSC resources in powershell.

You can refer to other similar articles as well

• Overview of PuppetDB
• Puppet Language
• Continuous Delivery for Puppet Enterprise
• Overview of Custom Facts in Puppet
• Configuration Management 
• Configuring PuppetDB

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