Puppet has changed the way we manage our systems.

When it was released, other configuration management tools were around, but it was clear that it had something special. It came at the right time with the right approach. The challenges of IT infrastructures were beginning to step up to a new level, and the need to automate common activities such as a quick setup and configuration of systems was becoming a requirement. Puppet presented a sane model, based on the abstraction of resources and the definition of the expected state of a system, using a clear and sysadmin-friendly language.

There are various books about Puppet around, and most of them are very good. This one tries to contribute with solid, no frills content (few pictures, few large blocks of copied and pasted text) and some new perspectives and topics. It begins with an intense technical overview of Puppet, Hiera, and PuppetDB, so that you can use them to design appropriate Puppet architectures that fit your IT infrastructure.

We will explore where our data can be placed, how to design reusable modules, and how they can be used as building blocks for higher abstraction classes. We will try to give a clearer and wider view of what it means to work with Puppet and what are the challenges to face when we introduce it in our systems, from code management to deployment rollouts. We will dive into Puppet's internals and its extension points, showing the multiple ways we can tweak, extend, and hack with it. We will also look at less traditional fields, such as Puppet as a configuration management tool for network devices or cloud services.

Since the first edition of this book was published by Alessandro in 2014, it has been a reference for both learners that wanted to start with Puppet and for experienced users that were looking for a deeper understanding of this tool. During these years, some things have changed in Puppet and the content of the book needed to be refreshed. Probably the most important release of Puppet till now, version 4, happened and it introduced some changes in several aspects. This edition covers the main differences that appeared with this new version, how it is installed, compatibility between versions, and so on. It also adds descriptions for the new language features so it can continue being used as a reference for learners of all levels. Some of the contents that may have become obsolete have been updated or replaced by new implementations or better practices. Some sections have been extended to provide further details on things that have proven to be of interest to the community. And in the last chapter, we will also analyze some of the steps Puppet is taking or will take in the future.