Variables and Facts

Variables and Facts

Variable Types

Playbook Variables

vars:
  http_port: 80
  max_clients: 200
  server_name: web01

vars_files:
  - vars/common.yml
  - vars/webserver.yml

Inventory Variables

[webservers]
web1.example.com http_port=8080 max_clients=100
web2.example.com http_port=8081 max_clients=200

[webservers:vars]
server_type=apache
env=production

Group Variables

# group_vars/webservers.yml
http_port: 80
max_clients: 200
server_type: nginx

# group_vars/all.yml
company_name: Example Corp
default_timezone: UTC

Variable Scope

Global Scope

• Role defaults
• Inventory variables
• Playbook variables
• Extra variables (highest precedence)

Host Scope

• Host inventory variables
• Host facts
• Registered variables

Play Scope

• Play variables
• Task variables
• Block variables

Ansible Facts

System Facts

- name: Display system facts
  debug:
    msg: |
      OS Family: {{ ansible_os_family }}
      Distribution: {{ ansible_distribution }}
      Version: {{ ansible_distribution_version }}
      Architecture: {{ ansible_architecture }}

Custom Facts

- name: Create custom fact directory
  file:
    path: /etc/ansible/facts.d
    state: directory

- name: Add custom fact file
  copy:
    content: |
      [application]
      version=1.2.3
      environment=production
    dest: /etc/ansible/facts.d/application.fact

Working with Variables

Variable Precedence

1. Command line extra vars
2. Task variables
3. Block variables
4. Role and include variables
5. Playbook variables
6. Inventory variables
7. Role defaults

Variable Usage

- name: Configure application
  template:
    src: app.conf.j2
    dest: "/etc/{{ app_name }}/config.conf"
  vars:
    app_name: myapp
    app_port: "{{ http_port | default(8080) }}"

Fact Gathering

Controlling Fact Gathering

---
- hosts: webservers
  gather_facts: yes  # or no
  tasks:
    - name: Show system memory
      debug:
        msg: "Total memory: MB"

Custom Fact Gathering

- name: Gather custom facts
  setup:
    filter: ansible_local

- name: Display custom facts
  debug:
    var: ansible_local

Best Practices

Variable Naming

• Use descriptive names
• Follow consistent naming conventions
• Use lowercase and underscores
• Prefix role variables

Variable Organization

• Group related variables
• Use separate variable files
• Document variable purposes
• Consider variable precedence

Practical Exercise

Working with Variables

1. Create variable files
2. Use variables in playbooks
3. Override variables
4. View variable precedence

Fact Management

1. Gather system facts
2. Create custom facts
3. Use facts in playbooks
4. Filter fact gathering

Key Takeaways

• Variables provide flexibility
• Facts offer system information
• Understand variable precedence
• Organize variables effectively

Additional Resources

• Variable Guide
• Facts Guide
• Variable Precedence