Ansible

Terraform builds the house (Server, VPC, DNS). Ansible furnishes the rooms (Installs Nginx, updates patches, creates users).

Ansible is a Configuration Management tool. It ensures that a group of servers matches a specific state.

Core Concepts

1. Agentless (Push Model)

Unlike Puppet or Chef, Ansible does not require an agent installed on the target server. It runs on your laptop (or CI server) and pushes commands over SSH.

2. Inventory

A simple text file listing the servers you want to manage.

[webservers]
192.168.1.50
192.168.1.51

[databases]
db-01.internal

3. Playbooks (YAML)

The declarative instructions. "Ensure Nginx is installed."

- name: Configure Webservers
  hosts: webservers
  become: true  # Run as sudo
  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present

    - name: Start Nginx
      service:
        name: nginx
        state: started

Idempotency

The most important word in Ansible.

• Imperative (Bash): apt-get install nginx. If you run this twice, it might error or try to reinstall.
• Declarative (Ansible): state: present. Ansible checks if Nginx is there. If yes, do nothing. If no, install it.

Ansible Roles

Don't write one giant Playbook. Roles allow you to package tasks, variables, and files into reusable components.

Directory Structure:

roles/
  nginx/
    tasks/main.yml
    templates/nginx.conf.j2
    vars/main.yml
  mysql/
    tasks/main.yml
playbook.yml

Terraform vs. Ansible

The Happy Marriage: Use Terraform to create the EC2 Instance. Pass the User Data script to bootstrap SSH. Then use Ansible to configure the application inside.