Variables

Ansible supports variables that can be used to store values that can then be reused throughout files in an Ansible project.

Naming Variables

Variable names must start with a letter, and they can only contain letters, numbers, and underscores. For example web_server.

Variables can be defined in a variety of places:

• Global scope
• Play scope
• Host scope

Defining Variables in Playbooks

A common method is to place a variable in a vars block at the beginning of a playbook:

- hosts: all
  vars:
    user: richard
    home: /home/richard

Or to define playbook variables in external files:

- hosts: all
  vars_files:
    - vars/packages.yml

Using Variables in Playbooks

When a variable is used as the first element to start a value, quotes are mandatory.

vars:
  user: richard

tasks:
  - name: Create user {{ user }}
    user:
      name: "{{ user }}"

Host Variables and Group Variables

Use directories to populate host and group variables by creating two directories group_vars and host_vars.

Example structure:

ansible
├── ansible.cfg
├── group_vars
│   ├── dc1
├── host_vars
│   ├── server.example.com
├── inventory
└── playbook.yml

Overriding Variables from the Command Line

Inventory variables are overridden by variables set in a playbook, which in turn may be overridden through arguments passed to the ansible or ansible-playbook commands on the command line. Variables set on the command line are called extra variables.

Example:

ansible-playbook main.yml -e "package=httpd"

Using Arrays as Variables

You cna also can use arrays, which are iterated over by ansible.

Example:

users:
  bjones:
    first_name: Joe
    last_name: Blogs
    home_dir: /users/jblogs
  acook:
    first_name: John
    last_name: Doe
    home_dir: /users/jdoe

These can be explicitly referenced like this:

users.jdoe.first_name

Registered Variables

Use the register statement to capture the output of a command:

---
- name: Install a package 
  hosts: all
  tasks:
    - name: Install package
      yum:
        name: httpd
        state: installed
      register: install_result

    - debug: var=install_result