YAML Basics for Ansible Beginners

YAML (“YAML Ain’t Markup Language”) is the backbone of Ansible playbooks. It is simple, human-readable, and designed for configuration tasks. Let’s walk through the basics to help new learners.

Structure of YAML Files

YAML files often start with three dashes (---) to mark the beginning of a document. This is optional in Ansible, but it’s considered good practice.

Key Features of YAML

1. Comments

Use # to add comments. These are ignored by the parser.

# This is a comment
name: John Doe  # Inline comment

2. Key-Value Pairs

The simplest data structure in YAML is a key-value pair:

name: John Doe
age: 30

Keys must be unique within the same level.

3. Strings

Strings can be written with or without quotes. Use quotes if the string contains special characters or spaces.

name: "John Doe"
title: Software Developer

4. Booleans

YAML supports boolean values, written as true/false or yes/no:

enabled: true
debug: no

5. Lists

Lists in YAML are ordered collections, written with dashes (-):

fruits:
  - Apple
  - Banana
  - Cherry

Or inline:

fruits: [Apple, Banana, Cherry]

6. Dictionaries

Dictionaries are collections of key-value pairs:

person:
  name: John Doe
  age: 30
  city: New York

You can also write them inline:

person: {name: John Doe, age: 30, city: New York}

7. Multi-Line Strings

For long strings, YAML provides two ways to write them:

Folded Style (`>`)

Collapses into a single line, keeping spaces:

address: >
  123 Main Street,
  Springfield, USA

Result:

123 Main Street, Springfield, USA

Literal Style (`|`)

Preserves line breaks:

description: |
  This is a multi-line string.
  The line breaks will be preserved.