Book Image

Puppet 4.10 Beginner's Guide - Second Edition

By : John Arundel
Book Image

Puppet 4.10 Beginner's Guide - Second Edition

By: John Arundel

Overview of this book

Puppet 4.10 Beginner’s Guide, Second Edition, gets you up and running with the very latest features of Puppet 4.10, including Docker containers, Hiera data, and Amazon AWS cloud orchestration. Go from beginner to confident Puppet user with a series of clear, practical examples to help you manage every aspect of your server setup. Whether you’re a developer, a system administrator, or you are simply curious about Puppet, you’ll learn Puppet skills that you can put into practice right away. With practical steps giving you the key concepts you need, this book teaches you how to install packages and config files, create users, set up scheduled jobs, provision cloud instances, build containers, and so much more. Every example in this book deals with something real and practical that you’re likely to need in your work, and you’ll see the complete Puppet code that makes it happen, along with step-by-step instructions for what to type and what output you’ll see. All the examples are available in a GitHub repo for you to download and adapt for your own server setup.
Table of Contents (20 chapters)
Puppet 4.10 Beginner's Guide Second Edition
About the Author
About the Reviewer
Customer Feedback

Querying Hiera

In Puppet manifests, you can use the lookup() function to query Hiera for the specified key (you can think of Hiera as a key-value database, where the keys are strings and values can be any type).

In general, you can use a call to lookup() anywhere in your Puppet manifests where you might otherwise use a literal value. The following code shows some examples of this (lookup2.pp):

$apache_pkg = lookup('apache_pkg')

unless lookup('apparmor_enabled') {
  exec { 'apt-get -y remove apparmor': }

notice("dns_allow_query enabled: ", lookup('dns_allow_query'))

Typed lookups

You can make your code more reliable and catch possible errors by specifying the required data type of the key you're looking up. For example, passing Boolean as the second argument to lookup() will cause Puppet to raise an error unless the retrieved value is of type Boolean (lookup_type.pp):

notice(lookup('apparmor_enabled', Boolean))

If you accidentally look up the wrong key, or mistype the value in the data file...