Ansible 101 : What It Is, How It Works, and Why It Matters

Apr 12, 2025

I recently started digging more into Infrastructure as Code (IaC) tools and Devops tools in general to gain skills and knowledge for my future internship. In this series of articles, I will go over multiple tools and topics. We will mainly cover the basics, concepts, and provide simple examples. If I end up doing a lab with a specific tool, I will publish an article for it.

Here we will cover one of the most popular IaC tools out there, Ansible. We will look at how it works, and where it fits in the world of IT automation.

What is Ansible ?

It’s an open-source automation tool used for configuration management, application deployment, and task automation. In short: it helps you manage a bunch of computers or servers from a central place, without needing to log into each one and run commands manually.

Think of it as scripting, but scalable, cleanly organized, and repeatable. Additionaly Ansible is agentless, it connects through SSH meaning it can still communicate with the devices without requiring an application or service to be installed on the managed machines.

The Basics

Playbooks : These are the yml/yaml files that will describe the tasks that Ansible will perform.
Hosts : This is our inventory of machines that we want to manage. You can group them, give them aliases, and define variables per group.
Modules : Built-in tools that do specific tasks, like managing users, installing packages, or handling files.
Idempotency : Instead from resintalling from scratch every time we update playbooks , Ansible will only check what needs to be changed.

Example snippet of a playbook :

- name: Install NGINX on Ubuntu
  hosts: webservers
  remote_user: ubuntu   
  become: true

  tasks:
    - name: Ensure NGINX is installed
      apt:
        name: nginx
        state: present

    - name: Ensure nginx is running
      service:
        name: nginx
        state: started
        enabled: true

This playbook checks if NGINX is installed on the webservers group, and if it is not, it will install it using the apt module (for Debian/Ubuntu). Then it ensures that NGINX is running by using the service module that can start/stop/restart services.

Example of hosts.yml :

webservers:
  hosts:
    first.example.com:
    second.example.com:
dbservers:
  hosts:
    one.example.com:
    two.example.com:
    three.example.com:

Here we declare the group webservers, which contains the machines first.example.com and second.example.com. So now everytime we call the webservers, it will take acount of both machines.

What are the use cases ?

Ansible is used pretty much everywhere in IT operations:

Server provisioning: Automatically set up new servers with the right software and configurations.
App deployment: Roll out your application across multiple machines with one single command.
CI/CD pipelines: Automate deployment as part of your build/release workflow.
Cybersecurity: Automate patching, enforce security baselines, or deploy honeypots and monitoring tools. It’s also Security hardening like enforcing firewall rules, disabling unnecessary services, or maintaining system compliance.

Ressources

Here are some additional resources for those who want to learn more about this tool :

Ansible community documentation
Red Hat Starter Guide
Installing Ansible