Ansible Roles - Role Variables

Introduction

In Ansible, roles are a way to organize playbooks and facilitate reusability. Role variables are crucial to define and control the behavior of roles. This lesson will delve into the types, usage, and best practices for role variables in Ansible.

Definition

Role variables are variables defined within the context of a role that can influence how tasks within that role operate. They allow for a flexible and dynamic configuration of roles based on their environment or usage context.

Types of Role Variables

Role variables can be categorized into the following types:

• Default Variables: Defined in the defaults/main.yml file of the role.
• Vars: Defined in the vars/main.yml file of the role.
• Extra Variables: Passed at runtime using the -e option in the command line.
• Inventory Variables: Defined in the inventory file or through host_vars/group_vars.

Usage

To use role variables effectively, follow these steps:

1. Define default variables in defaults/main.yml:

# defaults/main.yml
---
http_port: 80
max_clients: 200
                

2. Define role-specific variables in vars/main.yml:

# vars/main.yml
---
server_name: myserver.local
                

3. Use variables in your tasks:

# tasks/main.yml
- name: Ensure Apache is installed
  apt:
    name: apache2
    state: present

- name: Configure Apache
  template:
    src: httpd.conf.j2
    dest: /etc/apache2/sites-available/{{ server_name }}.conf
                

4. Override variables at runtime:

ansible-playbook site.yml -e "http_port=8080"
                

Best Practices

When working with role variables, consider the following best practices:

• Use descriptive names for variables to enhance readability.
• Document variables in your role to explain their purpose.
• Use defaults for optional variables to prevent errors.
• Avoid hardcoding values; prefer using variables instead.

FAQ