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Lab 005 - Facts¶

• In this section, we will cover Ansible Facts
• Ansible facts are “Ansible Scripts” and are one of the building blocks of Ansible.
• Ansible facts are data related to your remote systems, including operating systems, IP addresses, attached filesystems, and more.
• Ansible facts are gathered about target nodes (host nodes to be configured) and returned back to controller nodes.

How to View Facts?¶

You can view facts of a remote machine by running:

ansible all -m setup

🔹 Example Output (Truncated for brevity):

{
    "ansible_facts": {
        "ansible_distribution": "Ubuntu",
        "ansible_distribution_version": "22.04",
        "ansible_architecture": "x86_64",
        "ansible_memory_mb": {
            "real": {
                "total": 7989,
                "used": 2034
            }
        },
        "ansible_default_ipv4": {
            "address": "192.168.1.10",
            "netmask": "255.255.255.0",
            "gateway": "192.168.1.1"
        }
    }
}

How to Use Facts in Playbooks?¶

• Facts allows you to base your playbook logic on the properties of the target hosts.
• all facts are prefixed with ansible_x.

Example: Installing Packages Based on OS¶

---
- hosts: all
  tasks:
    - name: Install Nginx on Debian using APT
      ansible.builtin.apt:
        name: nginx
        state: present
      when: ansible_distribution == "Ubuntu"

    - name: Install Nginx on RedHat using DNF
      ansible.builtin.dnf:
        name: nginx
        state: present
      when: ansible_distribution == "CentOS"

Example: Conditional Execution Based on Memory¶

- name: Restart Service if Memory is Low
  ansible.builtin.service:
    name: my_service
    state: restarted
  when: ansible_memory_mb.real.total < 4000

Commonly Used Facts¶

System Information¶

Networking¶

Hardware¶

Disabling Fact Gathering¶

By default, Ansible gathers facts before running a playbook. To disable it:

- hosts: all
  gather_facts: no
  tasks:
    - name: Print a message
      debug:
        msg: "Facts gathering is disabled!"

Custom Facts¶

You can define custom facts by creating .fact files in /etc/ansible/facts.d/ on the managed host.

Example: Creating a Custom Fact¶

1️⃣ Create a file /etc/ansible/facts.d/custom.fact with:

[custom]
environment=production
app_version=1.2.3

2️⃣ Retrieve the fact in a playbook:

- hosts: all
  tasks:
    - debug:
        msg: "App version is {{ ansible_local.custom.app_version }}"

Summary¶

🔹 Ansible facts provide system details dynamically.
🔹 They are automatically gathered using the setup module.
🔹 Useful for conditional logic in playbooks.
🔹 Facts include OS, networking, CPU, memory, and more.
🔹 Custom facts can be created for customized automation.

• Print the IP addresses of all the machines
• Bonus - Try print the addresss of linux-server-2 only without modifying the inventory file.

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