Book Image

Chef Cookbook - Third Edition

By : Matthias Marschall
Book Image

Chef Cookbook - Third Edition

By: Matthias Marschall

Overview of this book

Chef is a configuration management tool that lets you automate your more cumbersome IT infrastructure processes and control a large network of computers (and virtual machines) from one master server. This book will help you solve everyday problems with your IT infrastructure with Chef. It will start with recipes that show you how to effectively manage your infrastructure and solve problems with users, applications, and automation. You will then come across a new testing framework, InSpec, to test any node in your infrastructure. Further on, you will learn to customize plugins and write cross-platform cookbooks depending on the platform. You will also install packages from a third-party repository and learn how to manage users and applications. Toward the end, you will build high-availability services and explore what Habitat is and how you can implement it.
Table of Contents (15 chapters)
Chef Cookbook - Third Edition
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Index

Creating custom Ohai plugins


Ohai is the tool used by a Chef client to find out everything about the node's environment. During a Chef client run, Ohai populates the node object with all the information it found about the node, such as its operating system, hardware, and so on.

It is possible to write custom Ohai plugins to query additional properties about a node's environment.

Tip

Please note that Ohai data isn't populated until after a successful chef-client run!

In this example, we will see how to query the currently active firewall rules with Ohai using iptables and make them available as node attributes.

Getting ready

Make sure you have iptables installed on your node. See the Managing firewalls with iptables recipe in Chapter 7, Servers and Cloud Infrastructure.

Make sure you have the chef-client cookbook available:

  1. Add the chef-client cookbook to your Berksfile:

    mma@laptop:~/chef-repo $ subl Berksfile
    cookbook 'chef-client'
    
  2. Add the chef-client cookbook to your node's run list:

    mma@laptop...