What is Ansible

Ansible is an open-source automation tool developed by Red Hat that simplifies configuration management, application deployment, orchestration, and infrastructure as code (IaC). It is designed to be minimal, consistent, and easy to learn, using human-readable YAML files to describe automation tasks.

A Brief History

2012 --- Michael DeHaan creates Ansible and releases it as open source
2013 --- Ansible, Inc. is founded to provide commercial support
2014 --- Ansible Galaxy launches as a community hub for sharing roles
2015 --- Red Hat acquires Ansible, Inc. for approximately $150 million
2017 --- Ansible Tower is rebranded; AWX (the open-source upstream) is released
2019 --- Ansible Collections are introduced to modularise content
2023 --- Ansible Lightspeed with IBM watsonx Code Assistant launches
Today --- Ansible is one of the most widely adopted automation tools in the DevOps ecosystem

Why Ansible?

1. Agentless Architecture

Unlike tools such as Chef or Puppet, Ansible does not require an agent to be installed on managed nodes:

Communicates over SSH (Linux/Unix) or WinRM (Windows)
No background daemons consuming resources on managed hosts
Reduces security surface --- fewer open ports and running services
Simplifies bootstrapping --- just need SSH access and Python

2. Push-Based Model

Ansible uses a push model by default:

Model	How It Works	Examples
Push	The control node pushes configuration to managed nodes on demand	Ansible
Pull	Agents on managed nodes periodically pull configuration from a server	Puppet, Chef

Tip: Ansible can also operate in a pull mode using ansible-pull, which clones a Git repository and runs a local playbook on a schedule.

3. Human-Readable Automation

Ansible uses YAML (Yet Another Markup Language) for its automation files, making them easy to read, write, and version-control:

- name: Install and start nginx
  hosts: webservers
  tasks:
    - name: Install nginx
      apt:
        name: nginx
        state: present

    - name: Start nginx service
      service:
        name: nginx
        state: started
        enabled: true

4. Idempotency

Ansible tasks are idempotent --- running them multiple times produces the same result. If a package is already installed or a service is already running, Ansible will not make unnecessary changes.

Configuration Management vs Orchestration

Concept	Description	Ansible Feature
Configuration Management	Ensuring servers are in a desired state	Playbooks, Roles
Orchestration	Coordinating tasks across multiple systems	Plays, serial, delegation
Provisioning	Creating infrastructure resources	Cloud modules, Terraform integration
Application Deployment	Deploying and updating applications	Playbooks, rolling updates

Ansible can handle all four, making it a versatile tool in the DevOps toolchain.

Ansible vs Other Tools

Feature	Ansible	Puppet	Chef	Salt
Architecture	Agentless (SSH)	Agent-based	Agent-based	Agent or agentless
Language	YAML	Puppet DSL	Ruby DSL	YAML / Jinja2
Model	Push (default)	Pull	Pull	Push and Pull
Learning Curve	Low	Medium	High	Medium
Master Required	No (control node only)	Yes (Puppet Server)	Yes (Chef Server)	Yes (Salt Master)
Idempotent	Yes	Yes	Yes	Yes
Windows Support	Yes (WinRM)	Yes	Yes	Yes

Key Terminology

Term	Definition
Control Node	The machine where Ansible is installed and from which automation is run
Managed Node	A target machine managed by Ansible (also called a host)
Inventory	A list of managed nodes organised into groups
Module	A unit of code that Ansible executes on managed nodes (e.g., `apt`, `copy`, `service`)
Task	A single action using a module
Play	A set of tasks applied to a group of hosts
Playbook	A YAML file containing one or more plays
Role	A reusable, self-contained collection of tasks, variables, files, and templates
Facts	System information automatically gathered from managed nodes
Handler	A task triggered by a notification from another task

How Ansible Works

Control Node                     Managed Nodes
+----------------+               +-----------------+
| ansible or     |  SSH/WinRM    | Target Host 1   |
| ansible-playbook| -----------> | (no agent)      |
|                |               +-----------------+
| Inventory      |               +-----------------+
| Playbooks      |  SSH/WinRM    | Target Host 2   |
| Roles          | -----------> | (no agent)      |
+----------------+               +-----------------+

You write a playbook describing the desired state
Ansible connects to managed nodes via SSH
Ansible copies small programs (modules) to the managed nodes
Modules execute, make changes if needed, and return results
Ansible removes the temporary modules and reports results

Use Cases

Server provisioning --- configure new servers with the right packages, users, and services
Application deployment --- deploy applications with zero-downtime rolling updates
Security hardening --- enforce security baselines across all servers
Cloud infrastructure --- provision and manage AWS, Azure, GCP, and other cloud resources
Network automation --- configure routers, switches, and firewalls
Container orchestration --- manage Docker, Kubernetes, and Podman environments
Compliance --- ensure systems comply with regulatory standards (PCI, HIPAA, SOC2)

Summary

Ansible is an agentless, push-based automation tool that uses human-readable YAML to describe infrastructure as code. Its low learning curve, idempotent design, and broad ecosystem make it one of the most popular tools in the DevOps landscape. In the next lesson, we will install Ansible and run our first commands.