Book Image

Ansible Playbook Essentials

By : Gourav Shah, GOURAV JAWAHAR SHAH
Book Image

Ansible Playbook Essentials

By: Gourav Shah, GOURAV JAWAHAR SHAH

Overview of this book

Ansible Playbook Essentials will show you how to write a blueprint of your infrastructure, encompassing multitier applications using Ansible's playbooks. Beginning with basic concepts such as plays, tasks, handlers, inventory, and YAML Ain't Markup Language (YAML) syntax that Ansible uses, you'll understand how to organize your code into a modular structure. Building on this, you will study techniques to create data-driven playbooks with variables, templates, logical constructs, and encrypted data, which will further strengthen your application skills in Ansible. Adding to this, the book will also take you through advanced clustering concepts, such as discovering topology information about other nodes in the cluster and managing multiple environments with isolated configurations. As you approach the concluding chapters, you can expect to learn about orchestrating infrastructure and deploying applications in a coordinated manner. By the end of this book, you will be able to design solutions to your automation and orchestration problems using playbooks quickly and efficiently.
Table of Contents (20 chapters)
Ansible Playbook Essentials
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Setting Up the Learning Environment
References
Index

Node discovery with magic variables


We have looked at user-defined variables as well as system data, that is, facts. In addition to these, there are a few variables that define the meta information about the nodes, inventory, and plays, for example, which groups a node belongs to, what groups are part of the inventory, which nodes belong to which group, and so on. These variables, which are implicitly set, are called magic variables, and are very useful for discovering nodes and topology information. The following table lists the most useful magic variables, and their description:

Magic Variable

Description

hostvars

These are lookup variables or facts set on another host.

groups

This is the list of groups in the inventory. This can be used to walk over a group of nodes to discover its topology information.

group_names

This is the list of groups that the node belongs to.

inventory_hostname

This is the hostname set in the inventory file. It can be different to the ansible_hostname...