Book Image

Mastering Ansible, 4th Edition - Fourth Edition

By : James Freeman, Jesse Keating
Book Image

Mastering Ansible, 4th Edition - Fourth Edition

By: James Freeman, Jesse Keating

Overview of this book

Ansible is a modern, YAML-based automation tool (built on top of Python, one of the world’s most popular programming languages) with a massive and ever-growing user base. Its popularity and Python underpinnings make it essential learning for all in the DevOps space. This fourth edition of Mastering Ansible provides complete coverage of Ansible automation, from the design and architecture of the tool and basic automation with playbooks to writing and debugging your own Python-based extensions. You'll learn how to build automation workflows with Ansible’s extensive built-in library of collections, modules, and plugins. You'll then look at extending the modules and plugins with Python-based code and even build your own collections — ultimately learning how to give back to the Ansible community. By the end of this Ansible book, you'll be confident in all aspects of Ansible automation, from the fundamentals of playbook design to getting under the hood and extending and adapting Ansible to solve new automation challenges.
Table of Contents (18 chapters)
1
Section 1: Ansible Overview and Fundamentals
7
Section 2: Writing and Troubleshooting Ansible Playbooks
13
Section 3: Orchestration with Ansible

Comparing values

Comparisons are used in many places with Ansible. Task conditionals are comparisons. Jinja2 control structures, such as if/elif/else blocks, for loops, and macros, often use comparisons; some filters use comparisons as well. To master Ansible's usage of Jinja2, it is important to understand what comparisons are available.

Comparisons

Like most languages, Jinja2 comes equipped with the standard set of comparison expressions you would expect, which will render a Boolean true or false.

The expressions in Jinja2 are as follows:

If you have written comparison operations in almost any other programming language (usually in the form of an if statement), these should all seem very familiar. Jinja2 maintains this functionality in templates, allowing for the same powerful comparison operations you would expect in conditional logic from any good programming language.

Logic

Sometimes, performing a single...