Book Image

Puppet 5 Cookbook - Fourth Edition

By : Thomas Uphill
Book Image

Puppet 5 Cookbook - Fourth Edition

By: Thomas Uphill

Overview of this book

Puppet is a configuration management system that automates all your IT configurations, giving you control of managing each node. Puppet 5 Cookbook will take you through Puppet's latest and most advanced features, including Docker containers, Hiera, and AWS Cloud Orchestration. Updated with the latest advancements and best practices, this book delves into various aspects of writing good Puppet code, which includes using Puppet community style, checking your manifests with puppet-lint, and learning community best practices with an emphasis on real-world implementation. You will learn to set up, install, and create your first manifests with version control, and also learn about various sysadmin tasks, including managing configuration files, using Augeas, and generating files from snippets and templates. As the book progresses, you'll explore virtual resources and use Puppet's resource scheduling and auditing features. In the concluding chapters, you'll walk through managing applications and writing your own resource types, providers, and external node classifiers. By the end of this book, you will have learned to report, log, and debug your system.
Table of Contents (16 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Using virtual resources


Virtual resources in Puppet might seem complicated and confusing but, in fact, they're very simple. They're exactly like regular resources, but they don't actually take effect until they're realized (in the sense of "made real"); a regular resource, on the other hand, can only be declared once per node (so two classes can't declare the same resource, for example). A virtual resource can be realized as many times as you like.

This comes in handy when you need to move applications and services between machines. If two applications that use the same resource end up sharing a machine, they will cause a conflict unless you make the resource virtual.

To clarify this, let's look at a typical situation where virtual resources might come in handy.

You are responsible for two popular web applications: WordPress and Drupal. Both are web apps running on Apache, so they both require the Apache package to be installed. The definition for wordpress might look something like the following...