YAML Overview

In this lesson, you will learn about YAML, a data serialization language commonly used in Ansible for creating playbooks and configuring applications. Understanding YAML is essential for effectively using Ansible, as it forms the basis of playbook creation. By the end of this lesson, you'll be familiar with the syntax and structure of YAML, and you'll understand how to use it to define complex configurations in a simple, human-readable format.

What is YAML?

YAML, which stands for "YAML Ain't Markup Language," is a human-readable data serialization format. It's used for configuration files and in data storage or transmission scenarios. The design of YAML focuses on simplicity and easy readability, which makes it highly popular in configuration management and application deployment, like in Ansible playbooks.

YAML files traditionally use the .yaml or .yml extension and are composed of key-value pairs.

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Ansible's official documentation tends to lead toward the .yml extension rather than the .yaml extension, so we will do the same with our YAML files while working with Ansible.

It is crucial to understand that YAML is sensitive to white spaces and indentation, which it uses to represent data hierarchy. This feature distinguishes YAML from other markup languages, which often use tags or brackets.

Basic Syntax and Structure

A YAML file starts with ---, representing the beginning of a document, and ends with three dots …, though these are optional in most cases. The basic structure involves key-value pairs, lists, and dictionaries. Let's explore these with examples.

Key-Value Pairs

The most basic element of YAML is the key-value pair. This pairs a key with a corresponding value, separated by a colon and a space.

In this example, user and password are keys, and john_doe and secure_password are their respective values.

Lists and Arrays

Lists…