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

Passing arguments to shell commands


The Chef client enables you to run shell commands by using the execute resource. However, how can you pass arguments to such shell commands? Let's assume you want to calculate a value and pass it to the shell command in your recipe. How can you do that? Let's find out...

Getting ready

Make sure you have a cookbook called my_cookbook, and that the run_list of your node includes my_cookbook, as described in the Creating and using cookbooks recipe in Chapter 1, Chef Infrastructure.

How to do it...

Let's see how we can pass Ruby variables into shell commands:

  1. Edit your default recipe. You'll pass an argument to a shell command by using an execute resource:

    mma@laptop:~/chef-repo $ subl   cookbooks/my_cookbook/recipes/default.rb
    max_mem = node['memory']['total'].to_i * 0.8
    
    execute 'echo max memory value into tmp file' do
      command "echo #{max_mem} > /tmp/max_mem"
    end
    
  2. Upload the modified cookbook to the Chef server:

    mma@laptop:~/chef-repo $ knife cookbook upload...