YAML Syntax¶

This page provides a basic overview of correct YAML syntax, which is how Ansible playbooks (our configuration management language) are expressed.

We use YAML because it is easier to read and write for humans than other common data formats like XML or JSON. Further, there are libraries available for reading and writing YAML in most programming languages.

You may also wish to read Playbooks at the same time to see how this is used in practice.

YAML Basics¶

For ansible, nearly every YAML file starts with a list. Each item in the list is a list of key/value pairs, commonly called a “hash” or a “dictionary”. So, we need to know how to write lists and dictionaries in YAML.

There’s another small quirk to YAML. All YAML files (regardless of their association with ansible or not) should start with ---. This is just a YAML format thing that means “this is the start of a document”.

All members of a list are lines beginning at the same indentation level starting with a - (dash) character:

---
# A list of tasty fruits
- Apple
- Orange
- Strawberry
- Mango

A dictionary is represented in a simple key: and value form:

---
# An employee record
name: John Eckersberg
job: Developer
skill: Elite

Dictionaries can also be represented in an abbreviated form if you really want to:

---
# An employee record
{name: John Eckersberg, job: Developer, skill: Elite}

Ansible doesn’t really use these too much, but you can also specify a boolean value (true/false) in several forms:

---
knows_oop: True
likes_emacs: TRUE
uses_cvs: false

Let’s combine what we learned so far in an arbitary YAML example. This really has nothing to do with Ansible, but will give you a feel for the format:

---
# An employee record
name: John Eckersberg
job: Developer
skill: Elite
employed: True
foods:
    - Apple
    - Orange
    - Strawberry
    - Mango
languages:
    ruby: Elite
    python: Elite
    dotnet: Lame

That’s all you really need to know about YAML to get started writing Ansible playbooks.