Context-Aware Automation with Ansible Facts

What are Ansible Facts?

Instead of hardcoding a server's IP address or manually checking if a server is RedHat or Ubuntu, Ansible queries the target host and builds a massive dictionary of variables called Facts.

Why are they important?

Facts make automation context-aware. You can write highly reusable playbooks that behave differently based on the system they are running against. For example: "If OS is Debian, use apt; if RedHat, use yum."

What data is collected?

Ansible collects hardware architecture, active IP addresses, hostname, total memory, disk space, network interfaces, and much more.

The Gathering Phase

The Execution Flow

• 1. Connect Ansible connects to the remote server via SSH (or WinRM).
• 2. Gather Ansible automatically runs the setup module behind the scenes to collect all system facts.
• 3. Execute Ansible runs your defined tasks, substituting any fact variables (like {{ ansible_hostname }}) with the collected data.

---
- hosts: web
  gather_facts: no
  tasks:
    - name: Install nginx
      apt:
        name: nginx
        state: present

Commands & Common Facts

You don't have to guess what facts are available. You can run an ad-hoc command using the setup module to dump the entire JSON payload of facts for any server.

terminal

# Manually view all collected facts from managed nodes
$ ansible all -m setup
server-01 | SUCCESS => {
    "ansible_facts": {
        "ansible_architecture": "x86_64",
        "ansible_hostname": "server-01",
        ...

Quick Recap