Ansible & Automation – Complete Masterclass Notes

⚙️ Ansible & Configuration Automation Masterclass

Agentless Architecture over SSH, YAML Playbooks, Static/Dynamic Inventories, Idempotency, Jinja2 Templating, Ansible Roles aur CI/CD Server Provisioning ka complete guide.

Module 01

1️⃣ What is Ansible & Agentless Architecture

Definition: Ansible Red Hat dwara maintained ek open-source configuration management, application deployment aur provisioning tool hai. Yeh target nodes par bina koi background daemon ya agent install kiye standard OpenSSH protocol ke zariye remotely commands execute karta hai.

Criteria	Ansible	Puppet / Chef
Architecture	Agentless (Push Model via SSH/WinRM)	Agent-based (Pull Model with background daemon)
Language	Python (Engine) + YAML (Human-readable playbooks)	Ruby / Custom DSL
Setup Overhead	Zero target overhead (Requires Python + SSH only)	Heavy client installation, TLS certs management

Module 02

2️⃣ Inventory Files: Static & Dynamic

Ansible control node ko batata hai ki kin managed servers par tasks run karne hain:

# Static Inventory (hosts.ini)
[webservers]
web1.fresherjobsalert.com ansible_host=13.233.20.11
web2.fresherjobsalert.com ansible_host=13.233.20.12

[dbservers]
db1.fresherjobsalert.com  ansible_host=10.0.4.55

[production:children]
webservers
dbservers

[all:vars]
ansible_user=ubuntu
ansible_ssh_private_key_file=~/.ssh/prod_id_rsa

Module 03

3️⃣ Ad-Hoc Commands & Core Modules

Bina playbook likhe single one-liner tasks execute karna:

# 1. Connectivity Ping Test across all nodes
ansible all -i hosts.ini -m ping

# 2. Check Disk Space
ansible webservers -i hosts.ini -m command -a "df -h"

# 3. Install Nginx using privileged sudo
ansible webservers -i hosts.ini -b -m apt -a "name=nginx state=present update_cache=yes"

Module 04

4️⃣ YAML Playbooks & Idempotency

Idempotency: Ansible ka primary design pillar. Agar server par Nginx pehle se installed aur running hai, toh playbook dubara run karne par Ansible kuch modify nahi karega aur ok return karega bina unnecessary service restart kiye.

---
- name: Deploy Production Nginx Web Server
  hosts: webservers
  become: yes
  tasks:
    - name: Ensure Nginx is installed
      ansible.builtin.apt:
        name: nginx
        state: present

    - name: Ensure Nginx service is running & enabled at boot
      ansible.builtin.service:
        name: nginx
        state: started
        enabled: yes
      notify: Reload Nginx

  handlers:
    - name: Reload Nginx
      ansible.builtin.service:
        name: nginx
        state: reloaded

Live Ansible Playbook Execution & Idempotency Simulator

[Ansible Control Node]: Ready. Inventory loaded: 2 nodes [web1, web2]. Click an execution scenario above...

Module 05

5️⃣ Variables, Facts & Jinja2 Templates

Ansible Facts: Playbook run hote hi control node target machine ke hardware metadata (IP, OS version, RAM, CPU cores) ko ansible_facts me dynamically gather karta hai.
Jinja2 Templating (.j2): Dynamic configuration files generate karne ke liye curly-brace syntax ({{ variable_name }}).

# nginx.conf.j2 template snippet
server {
    listen {{ http_port | default(80) }};
    server_name {{ server_domain }};
    root /var/www/html;
    worker_processes {{ ansible_facts['processor_vcpus'] }};
}

Module 06

6️⃣ Loops, Conditionals & Vault Security

# 1. Loops (Installing multiple packages)
- name: Install developer utilities
  ansible.builtin.apt:
    name: "{{ item }}"
    state: present
  loop:
    - git
    - curl
    - htop
    - fail2ban

# 2. Conditionals (when clause)
- name: Restart RedHat firewalld
  ansible.builtin.service:
    name: firewalld
    state: restarted
  when: ansible_facts['os_family'] == "RedHat"

# 3. Encrypting sensitive passwords with Ansible Vault
# ansible-vault encrypt secrets.yml

Module 07

7️⃣ Ansible Roles & Directory Architecture

Large enterprise projects ko modularize karne ke liye standard folder layout (ansible-galaxy init my_role):

my_role/
├── tasks/        # Main list of tasks (main.yml)
├── handlers/     # Service restart handlers (main.yml)
├── templates/    # Jinja2 configuration templates (.j2)
├── files/        # Static files transferred as-is
├── vars/         # Role-specific high priority variables
├── defaults/     # Default low priority fallback variables
└── meta/         # Role dependencies and author metadata

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