Ansible Set Hostname from Fact

Ansible is an open-source automation tool that helps to manage IT infrastructure, applications, and network services. With Ansible, you can automate complex IT tasks such as configuration management, application deployment, and cloud provisioning.

One of the powerful features of Ansible is its ability to gather facts about the target hosts. These facts can be used in creating dynamic inventories or for debugging purposes.

In this article, we will explore how to use Ansible to set the hostname of a target host based on a fact.

Prerequisites

Before we proceed, make sure that you have the following:

• Ansible installed on your control machine
• Access to one or more target hosts

Steps

Step 1: Gathering Host Facts

The first step is to gather facts about the target host. You can use the setup module to gather all the facts or you can specify only the facts that you need. Here's an example:

- name: Gather facts
  hosts: target_host
  tasks:
    - name: Gather all facts
      setup:

    - name: Get hostname fact
      debug:
        var: ansible_hostname

The above playbook will gather all the facts about target_host and print the ansible_hostname variable.

Step 2: Set Hostname using Facts

Once you have the hostname fact, you can use the hostname module to set the hostname of the target host.

- name: Set hostname using facts
  hosts: target_host
  tasks:
    - name: Gather all facts
      setup:

    - name: Set hostname
      hostname:
        name: "{{ ansible_hostname }}"

The above playbook will set the hostname of target_host to ansible_hostname fact.

Step 3: Verify Hostname

To verify that the hostname has been set correctly, you can use the assert module to compare the expected hostname with the actual hostname.

- name: Verify hostname
  hosts: target_host
  tasks:
    - name: Gather all facts
      setup:

    - name: Set hostname
      hostname:
        name: "{{ ansible_hostname }}"

    - name: Verify hostname
      assert:
        that:
          - ansible_hostname == ansible_fqdn

The above playbook will set the hostname of target_host to ansible_hostname fact and then verify that the hostname has been set correctly.

Conclusion

In this article, we learned how to use Ansible to set the hostname of a target host based on a fact. Gathering facts and using them in automation can greatly increase the efficiency and accuracy of your IT workflows.