Skip to main content

Using Ansible Facts

# Using Ansible Facts

Ansible Facts are valuable data returned by Ansible from its target nodes when it runs a playbook. It gives us detailed information about the system or node. This data can be used to configure the system based on its current state.

## Gathering Facts

By default, Ansible automatically runs the setup module before executing tasks in a playbook. This setup module is responsible for gathering facts about the system.

```yaml
---
- hosts: all
  tasks:
    - name: Display all facts
      debug:
        var: ansible_facts

The above playbook will display all the facts gathered from the target node.

Using Facts​

Once the facts are gathered, we can use them in our playbook. For example, let's use the ansible_distribution fact that contains the name of the OS distribution.

---
- hosts: all
  tasks:
    - name: Check if the OS is Ubuntu
      debug:
        msg: "This is an Ubuntu system"
      when: ansible_facts['os_family'] == "Debian"

In this playbook, the debug message will only be displayed if the operating system is a Debian-based one, like Ubuntu.

Disabling Fact Gathering​

There are scenarios where we might not want to gather facts. We can disable the fact gathering by setting gather_facts to no.

---
- hosts: all
  gather_facts: no
  tasks:
    - name: This will not gather facts
      debug:
        msg: "Facts are not gathered"

Custom facts​

Ansible allows you to deal with custom facts. These are facts you define for your hosts, not gathered by Ansible. For example, you can set a fact for the application version.

---
- hosts: all
  tasks:
    - name: Set custom fact
      set_fact:
        app_version: "1.0.0"

Then, you can use this fact in later tasks or templates.

Facts Caching​

Caching facts can be beneficial when dealing with large inventories or complicated playbooks. To enable fact caching, add the following to ansible.cfg:

[defaults]
fact_caching = jsonfile
fact_caching_connection = /tmp/ansible_fact_cache
fact_caching_timeout = 86400

After setting this, Ansible will store gathered facts in JSON files in the directory specified by fact_caching_connection for the time specified by fact_caching_timeout.

In conclusion, Ansible Facts are a powerful tool that allows you to tailor your configuration management to the state of your systems. They can be used out of the box, disabled, and even customized to suit your needs.