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

Comparing package versions


Package version numbers are odd things. They look like decimal numbers, but they're not: a version number is often in the form 2.6.4, for example. If you need to compare one version number with another, you can't do a straightforward string comparison: 2.6.4 would be interpreted as greater than 2.6.12. And a numeric comparison won't work because they're not valid numbers.

Puppet's versioncmp function comes to the rescue. If you pass two things that look like version numbers, it will compare them and return a value indicating which is the greater:

versioncmp( A, B )

returns:

  • 0 if A and B are equal

  • Greater than 1 if A is higher than B

  • Less than 0 if A is less than B

How to do it…

Here's an example using the versioncmp function:

  1. Modify your manifests/nodes.pp file as follows:

    node 'cookbook' {
      $app_version = '1.2.2'
      $min_version = '1.2.10'
    
      if versioncmp($app_version, $min_version) >= 0 {
        notify { 'Version OK': }
      } else {
        notify { 'Upgrade needed': }
      }...