Book Image

Puppet 3 Cookbook - Second Edition

By : John Arundel
Book Image

Puppet 3 Cookbook - Second Edition

By: John Arundel

Overview of this book

A revolution is happening in web operations. Configuration management tools can build servers in seconds, and automate your entire network. Tools like Puppet are essential to taking full advantage of the power of cloud computing, and building reliable, scalable, secure, high-performance systems. More and more systems administration and IT jobs require some knowledge of configuration management, and specifically Puppet."Puppet 3 Cookbook" takes you beyond the basics to explore the full power of Puppet, showing you in detail how to tackle a variety of real-world problems and applications. At every step it shows you exactly what commands you need to type, and includes full code samples for every recipe.The book takes the reader from a basic knowledge of Puppet to a complete and expert understanding of Puppet's latest and most advanced features, community best practices, writing great manifests, scaling and performance, and extending Puppet by adding your own providers and resources. It starts with guidance on how to set up and expand your Puppet infrastructure, then progresses through detailed information on the language and features, external tools, reporting, monitoring, and troubleshooting, and concludes with many specific recipes for managing popular applications.The book includes real examples from production systems and techniques that are in use in some of the world's largest Puppet installations, including a distributed Puppet architecture based on the Git version control system. You'll be introduced to powerful tools that work with Puppet such as Hiera. The book also explains managing Ruby applications and MySQL databases, building web servers, load balancers, high-availability systems with Heartbeat, and many other state-of-the-art techniques
Table of Contents (16 chapters)
Puppet 3 Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Making quick edits to config files


When you need to have Puppet change a particular setting in a config file, it's common to simply deploy the whole file with Puppet. This isn't always possible, though; especially if it's a file which several different parts of your Puppet manifest may need to modify.

What would be useful is a simple recipe to add a line to a config file if it's not already present, for example, adding a module name to /etc/modules to tell the kernel to load that module at boot. You can use an exec resource to do jobs like this.

How to do it…

This example shows how to use exec to append a line to a text file:

  1. Add the following code to your manifests/site.pp file:

    define append_if_no_such_line($file,$line) {
      exec { "/bin/echo '${line}' >> '${file}'":
        unless => "/bin/grep -Fx '${line}' '${file}'",
      }
    }
  2. Modify your manifests/nodes.pp file as follows:

    node 'cookbook' {
      append_if_no_such_line { 'enable-ip-conntrack':
        file => '/etc/modules',
        line => 'ip_conntrack...