Book Image

Puppet Cookbook - Third Edition - Third Edition

By : Thomas Uphill, John Arundel
Book Image

Puppet Cookbook - Third Edition - Third Edition

By: Thomas Uphill, John Arundel

Overview of this book

This book is for anyone who builds and administers servers, especially in a web operations context. It requires some experience of Linux systems administration, including familiarity with the command line, file system, and text editing. No programming experience is required.
Table of Contents (12 chapters)
11
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"); whereas a regular resource 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 would 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:

class...