Puppet is a configuration management tool that has enjoyed phenomenal growth over the last few years. Propelled by increasing demands on sysadmins, and the continuous growth of infrastructure (both physical and virtual), Puppet has been one of the key technology components of the DevOps movement. This cultural shift focuses on breaking down the silo between development and operations. Tools like Puppet are important to this movement because it allows application deployment knowledge to be expressed as code to build automated release platforms.

Puppet is also helping lead the path towards software-defined infrastructure (or infrastructure as code). As more systems in data centers support better APIs, the importance of centralized configuration management increases. Puppet is leading this trend by leveraging its model to manage more than the roles of individual systems. It also supports network devices, load balancers, and managing virtual machine instances.

All system configurations in Puppet are expressed as resources that model complex configurations using Puppet’s Domain Specific Language (DSL). Puppet supports a large set of native resources for modeling the desired state of a system. Resources already exist for managing most common elements of a system (users, groups, packages, services). These native resources are implemented in Ruby using Puppet’s type and provider APIs.

The power of Puppet lies in its ability to manage the state of complex systems using this simple resource model. This book discusses the highly extensible resource model and the framework around it. It explores the extension points and how to leverage them to expand Puppet’s functionality.