Puppet 4: Working with Modules and Classes

UNDERSTANDING MODULES AND CLASSES

by scmGalaxy.com

About Me !

Module Overview

• Lab Environment
• Pluralsight Courses
• Course Contents

Lab Environment

Puppet 4 Series

This course follows on from the Puppet 4: Language Essentials and in this course you will learn to create Puppet Modules and use Puppet Classes. This will simplify your manifests and help make your code easier to maintain.

• Puppet 4: Language Essentials
• Puppet 4: Working with Modules and Classes
• Puppet 4: Working with Files and Templates
• Puppet 4: Hiera the Single Source of Truth
• Puppet 4: Server and Puppet Enterprise

Puppet 4: Working with Modules and Classes

Demo

Browsing the Puppet Forge

Summary

Puppet Forge

• https://forge.puppet.com
• Documentation
• Project URL
• puppet module install <module name>

Next up: Working with Puppet Environments

Working with Puppet Environments

Objectives

• What are Environments
• Creating an Environments
• Puppet Modules and Environments

Puppet Environments

The only default environment is Production but we may create more environments to isolate code between clients.

Puppet Environments

Discover Environments

sudo puppet module list
sudo puppet module install puppetlabs/ntp
sudo puppet module list
sudo puppet module uninstall puppetlabs/ntp
sudo puppet module install puppetlabs/ntp \
-i /etc/puppetlabs/code/modules

Modules and Environments

Puppet modules can be located in either the environment directory or a common shared directory. Modules that need to be accessed in more than one environment need to be installed into a common path.

Working with Modules and Environments

sudo mkdir -p \
 /etc/puppetlabs/code/environments/dev/{modules,manifests}
	
sudo puppet module install puppetlabs/ntp \
 --environment dev

Create an Environment

When installing modules if we have created custom environments we can install into the desired environment using the --environment option.

Create a Development Environment

• /etc/puppetlabs/code/environments
• /etc/puppetlabs/code/modules
• sudo puppet config print environment
• sudo puppet config set environment dev

Next up: Working with Modules

Working with Modules

Objectives

• Module Structure
• Manually Creating Modules
• Generating Modules

Puppet Modules

A Puppet module is simply a directory tree with specific and predictable content

<environment>/modules

ntp/
	manifests/init.pp
	files/
	lib/  
	facts.d/ 	
	templates/ 	
	examples/

cd /etc/puppetlabs/code/environments/production/modules				
sudo mkdir -p motd/{manifests,files,examples}

Create Simple Module

We can create a simple module to show how they are populated and used.

cd /etc/puppetlabs/code/environments/production/modules
sudo vim motd/manifests/init.pp  
class motd {
  file { ‘/etc/motd’:
	ensure  => ‘file’,
	content => file(‘motd/message’),
  }
}

Manifests

The <module>/mainifests/init.pp must contain a class with the same name as the module.

cd /etc/puppetlabs/code/environments/production/modules
sudo vim motd/files/message

Welcome to my server
Please play nicely

Files

The files directory can be used for file downloads or we can use the file function to copy the content of a file to a file resource. The function is used as: content => file(<module>/<files>/).

This relates to the path: <module>/<files>/<file>

cd /etc/puppetlabs/code/environments/production/modules
sudo vim motd/examples/init.pp
include motd

Examples

The examples directory can be used to show examples of module usage. The manifest name in not important but is often init.pp.

Create Simple Module

cd /etc/puppetlabs/code/environments/production/modules

sudo puppet module generate andrew/test
or
sudo puppet module generate andrew/test --skip-interview

Modules Metadata

Especially if modules are going to be longer lived, then we will also need to create metadata for our modules. We can create the files manually but we can use the puppet module generate command.

Generate Modules

<environment>/modules
<modulename>/manifests/init.pp
class motd {
}

content => file(‘motd/message’)
motd/files/message
puppet module generate user/module

Next up: Working with Puppet Classes

Working with Puppet Classes

Objectives

• Developing the NTP module
• Creating and using sub-classes

NTP Manifest

We have the NTP manifest from the previous Puppet 4: Language Essentials course. We can use this as our starting point for our NTP module.

cd /etc/puppetlabs/code/environments/production/modules		
sudo mkdir -p ntp/{files,manifests,examples} 
sudo cp ~/ntpfinal.pp ntp/manifests/init.pp			
Add class detail to surround existing code

Step 1

We can take to existing manifest and copy it to the init.pp of a new module.

Remove file content from init.pp	
Add to ntp/files/ntp.conf

Step 2

Create NTP Module

cd /etc/puppetlabs/code/environments/production/modules	
sudo vim ntp/manifests/config.pp 
class ntp::config {
…
}

Sub-Classes

We can create additional manifests with their own class definitions. These are known as sub-classes. The manifest name must match the class name. The double colon is used to separate name-spaces.

Create Sub-Classes

cd /etc/puppetlabs/code/environments/production/modules
sudo vim motd/files/message

Welcome to my server  
Please play nicely

Files

The files directory can be used for file downloads or we can use the file function to copy the content of a file to a file resource. The function is used as: content => file(<module>/<file>).

This relates to the path: <module>/<file>/<file>

cd /etc/puppetlabs/code/environments/production/modules			
sudo vim motd/examples/init.pp
include motd

Examples

The examples directory can be used to show examples of module usage. The manifest name in not important but is often init.pp.

cd /etc/puppetlabs/code/environments/production/modules
sudo puppet module generate andrew/test
or
sudo puppet module generate andrew/test --skip-interview

Modules Metadata

Especially if modules are going to be longer lived, then we will also need to create metadata for our modules. We can create the files manually but we can use the puppet module generate command.

Generate Modules

Sub-classes allow for us to abstract code to specific areas that they relate to, creating simpler code that is easier to maintain.

Classes and Manifests

Next up: Implementing Parameterized Classes

Implementing Parameterized Classes

Objectives

• Customizing input to classes
• Declaring classes with the include style and the resource style
• Validating input with standard library functions

Adding Flexibility

If we build in parameters to classes we can add flexibility to the code without having to write more classes or manifests.

Parameterized Classes

cd /etc/puppetlabs/code/environments/production/modules				
sudo vim motd/manifests/init.pp
class motd ( $motd_message = ‘Daily’ ) { 
 
   file { ‘/etc/motd’:
	ensure  => ‘present’,
	content => file(“motd/${motd_message}”),
   }
}

$motd_message #As no value is set this becomes a required 
parameter that we must supply a value for when declaring the class

$motd_message = ‘Daily’ #As we have supplied a default 
value the parameter is optional

String $motd_message = ‘Daily’ #We now enforce that the 
supplied value  must be a string.

Input Parameters and Values

We can make parameters mandatory or optional choosing to supply a default value or not. More than one parameter can be required and they become comma separated.

Adding Parameters

include motd
#We cannot pass parameters directly. We either have to 
accept the defaults or use external tools such as Hiera to 
populate the parameters.

Declaring Classes with Include

As we have seen so far we can declare classes using include.

class { ‘motd’: } 
#Use the default parameter values 
class { ‘motd’:
  motd_message => ‘Weekly’,
}
#Pass parameter values directly.

Declaring Classes like a Resource

We can also declare classes like we would a resource. This becomes more flexible but we must make sure each class is declared just once as with a resource.

Passing Parameters to Classes

#validate_re(<string_to_test>,<regular_expresssion>)				
$allowed_files = [ ‘^Daily$’, ‘^Weekly$’, ]
validate_re($motd_message, $allowed_files)

Validating Input

We can validate the input values using one of the many validation functions in the puppetlabs/stdlib. He we check the input against a list of allowed files.

Validating Input

Validating Input

Questions !!

Thanks !!