YAML

YAML

  • Yet Another Markup Language

  • 2001

  • Natural and Meaningful (Human Readable)

  • DataTypes

    • Scalars, Lists, Arrays

  • Data Structures

    • Indentation, dahses, colons

  • Common uses

    • Config files
    • Storing data

YAML only supports spaces Supports Unicode

Two styles:

  • Block styles Better for humans Less Compact
host: phl-42
datacenter:
  location: Phil
  cab: 14
roles:
  - web
  - some toher
  • Flow styles Compact, extension of json, folding, tags and anchors
host: "phl-42"
datacenter: {location: Phil, cab: 14} # need to be on same line and commas between values
roles: [web,some toher]

Mappings, Sequences

host: phl-42 # space between key: value is important
datacenter:
  location: phil #2 space indentations
  cab: 13
roles: 
  - webserver
  - wp_database # sequences cannot be wihtout mapping or blank

Scalars

String, number, or boolean

String: ” or "", double string allows for escape sequence Multiline: | or > Lots of multiline string

Structures

You can add multiple directives/documents in one files

add --- to the top of file when building multidocument file

e.g.

---
host: phl2
---
host: someother

Comments

# octothorpe space and the comment to add a comment in YAML

Tags

  • Setting a cstom URI
  • Setting local tags
  • Setting a data type
host: phl-42
datacenter:
  location: phil
  cab: !!str 13 # !!str changes the datatype to str more !!int !!float
roles: 
  - webserver
  - wp_database

Anchors

Anchors allow to store and reuse data

host: phl-42
datacenter:
  location: &PHL phil # now can referrence this anywhere with *PHL
  cab: !!str 13 # !!str changes the datatype to str more !!int !!float
roles: 
  - webserver
  - wp_database

Wrote a simple YAML file for ansible to install MariaDB

---
- hosts: localhost
  remote_user: ansible
  become: yes
  become_method: sudo
  connection: ssh
  gather_facts: yes
  tasks:
    - name: Installing MariaDB
      yum:
        name: mariadb-server
        state: latest
      notify:
        - startservice
  handlers:
    - name: startservice
      service:
        name: mariadb
        state: restarted