Book Image

Puppet 5 Cookbook - Fourth Edition

By : Thomas Uphill
Book Image

Puppet 5 Cookbook - Fourth Edition

By: Thomas Uphill

Overview of this book

Puppet is a configuration management system that automates all your IT configurations, giving you control of managing each node. Puppet 5 Cookbook will take you through Puppet's latest and most advanced features, including Docker containers, Hiera, and AWS Cloud Orchestration. Updated with the latest advancements and best practices, this book delves into various aspects of writing good Puppet code, which includes using Puppet community style, checking your manifests with puppet-lint, and learning community best practices with an emphasis on real-world implementation. You will learn to set up, install, and create your first manifests with version control, and also learn about various sysadmin tasks, including managing configuration files, using Augeas, and generating files from snippets and templates. As the book progresses, you'll explore virtual resources and use Puppet's resource scheduling and auditing features. In the concluding chapters, you'll walk through managing applications and writing your own resource types, providers, and external node classifiers. By the end of this book, you will have learned to report, log, and debug your system.
Table of Contents (16 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Using an external node classifier


When Puppet runs on a node, it needs to know which classes should be applied to that node. For example, if it is a web server node, it might need to include an Apache class. The normal way to map nodes to classes is in the Puppet manifest itself, for example, in your site.pp file:

node 'web1' {
  include apache
}

Alternatively, you can use an External Node Classifier (ENC) to do this job. An ENC is any executable program that can accept the fully-qualified domain name (FQDN) as the first command-line argument ($1). The script is expected to return a list of classes, and parameters, and an optional environment to apply to the node. The output is expected to be in the standard YAML format. When using an ENC, you should keep in mind that the classes applied through the standard site.pp are merged with those provided by the ENC.

Parameters returned by the ENC are available as top-scope variables to the node.

An ENC could be a simple shell script, for example, or...