Ansible Automation Guide | Generated by AI

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What is Ansible?

Ansible is an open-source automation tool that automates:

It is agentless (no software/agent needed on managed nodes), uses SSH (or WinRM for Windows), and is written in YAML (human-readable format).
Ansible is part of Red Hat and is one of the most popular DevOps tools today.

Key Advantages

Core Concepts

Concept Description
Inventory List of managed hosts (IP or hostname). Can be static (ini/yaml) or dynamic.
Playbook YAML file containing one or more plays. This is where you write automation.
Play Maps a group of hosts to tasks/roles.
Task Single action (e.g., install package, copy file, restart service).
Module Reusable code that performs a specific action (package, service, file, template, etc.).
Role Reusable directory structure of tasks, variables, templates, handlers, etc.
Handler Special task that runs only when notified by another task (e.g., restart nginx).
Facts Information gathered from remote hosts (OS, IP, memory, etc.).
Variables Customize playbooks (host vars, group vars, role vars, extra vars, etc.).

Installation

On control node (your laptop/server)

# Ubuntu/Debian
sudo apt update && sudo apt install ansible -y

# RHEL/CentOS/Rocky
sudo dnf install ansible -y

# macOS (with Homebrew)
brew install ansible

# Or use pip (recommended for latest version)
python3 -m pip install --user ansible

Check version:

ansible --version

Inventory

Simple INI format (inventory.ini)

[webservers]
web1.example.com
web2.example.com ansible_user=ubuntu ansible_ssh_private_key_file=~/.ssh/mykey.pem

[dbservers]
db1.example.com ansible_host=192.168.1.50

[all:vars]
ansible_python_interpreter=/usr/bin/python3

YAML format (inventory.yaml)

all:
  hosts:
    localhost:
      ansible_connection: local
  children:
    webservers:
      hosts:
        web1.example.com:
        web2.example.com:
          ansible_user: ubuntu
    dbservers:
      hosts:
        db1.example.com:

Test connectivity:

ansible all -i inventory.ini -m ping

First Ad-Hoc Command Examples

# Gather facts
ansible webservers -m setup

# Install nginx on all webservers
ansible webservers -m apt -a "name=nginx state=present" --become

# Copy file
ansible webservers -m copy -a "src=/local/file.txt dest=/remote/file.txt"

# Reboot servers
ansible all -m reboot --become

Writing Your First Playbook

Create first_playbook.yml:

---
- name: Configure web servers
  hosts: webservers
  become: yes                     # sudo
  vars:
    http_port: 80
    domain: example.com

  tasks:
    - name: Ensure nginx is installed
      apt:
        name: nginx
        state: present
        update_cache: yes

    - name: Copy nginx config file
      template:
        src: templates/nginx.conf.j2
        dest: /etc/nginx/sites-available/
      notify: Restart nginx

    - name: Enable new site
      file:
        src: /etc/nginx/sites-available/
        dest: /etc/nginx/sites-enabled/
        state: link

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

  handlers:
    - name: Restart nginx
      service:
        name: nginx
        state: restarted

Run it:

ansible-playbook -i inventory.ini first_playbook.yml

Common & Useful Modules

Category Modules Example Use
Packages apt, yum, dnf, pacman, pip Install software
Files file, copy, template, lineinfile, find Manage files/directories
System service, systemd, user, group, reboot Manage services, users
Command command, shell, script Run arbitrary commands
Cloud ec2instance, digital_ocean, azure_rm* Provision cloud resources
Database postgresql_db, mysql_db, mongodb_user Manage databases
Version Control git Checkout code
Facts setup Gather system info

Variables & Facts

Variable precedence (highest to lowest)

  1. Command line -e "var=value"
  2. Role defaults
  3. Inventory variables
  4. Play vars
  5. Host facts / gathered facts

Example using variables

vars:
  app_name: myapp
  app_user: www-data

vars_files:
  - secrets.yml

tasks:
  - name: Create app user
    user:
      name: ""
      shell: /bin/bash

Using facts

- name: Show OS distribution
  debug:
    msg: "This is  "

Conditionals & Loops

When (conditional)

tasks:
  - name: Install Apache on RedHat only
    yum:
      name: httpd
      state: present
    when: ansible_facts['os_family'] == "RedHat"

Loops

- name: Create multiple users
  user:
    name: ""
    state: present
  loop:
    - alice
    - bob
    - charlie

- name: Install list of packages
  apt:
    name: ""
    state: present
  loop: ""
  vars:
    packages:
      - nginx
      - git
      - vim

Roles – Best Practice Structure

myrole/
├── defaults/
│   └── main.yml
├── vars/
│   └── main.yml
├── tasks/
│   └── main.yml
├── handlers/
│   └── main.yml
├── templates/
│   └── nginx.conf.j2
├── files/
├── meta/
│   └── main.yml
└── README.md

Use roles in playbook:

- hosts: webservers
  roles:
    - common
    - nginx
    - myapp

Find thousands of ready roles:

ansible-galaxy search postgres
ansible-galaxy install geerlingguy.postgres

Real-World Use Cases

Use Case Typical Playbook/Role Example
Server bootstrapping Install base packages, create users, SSH keys, firewall
Web application deployment Git checkout → pip install → gunicorn → nginx reverse proxy
Database setup Install PostgreSQL/MySQL → create DB/user → restore dump
Continuous Deployment Triggered by webhook → pull latest code → run tests → deploy
Cloud provisioning Launch EC2 instances, add to load balancer, install app
Security hardening CIS benchmark roles, disable root login, update packages
Monitoring setup Install Prometheus/Node exporter, Grafana, Alertmanager
Backup automation rsync/dump databases → copy to S3 → cleanup old backups
Multi-environment management dev/staging/prod with different variables

Best Practices

  1. Always use roles for reusable code
  2. Use ansible-vault to encrypt sensitive data 
    ansible-vault create secrets.yml
ansible-playbook site.yml --ask-vault-pass
  3. Use Git to version control your playbooks/roles
  4. Use --check mode first (dry-run) 
    ansible-playbook site.yml --check
  5. Tag your tasks for selective runs 
    tags: ['nginx', 'web']

    Run: ansible-playbook site.yml --tags web

  6. Use pre_tasks and post_tasks when needed
  7. Never hardcode passwords – use vault or lookup plugins

Useful Commands Summary

ansible all -m ping
ansible all -m setup                    # gather facts
ansible-playbook playbook.yml --check   # dry run
ansible-playbook playbook.yml -t nginx  # run specific tag
ansible-vault encrypt secrets.yml
ansible-galaxy role install geerlingguy.nginx
ansible-galaxy collection install community.docker

Learning Resources

Start small → write ad-hoc commands → simple playbooks → roles → full infrastructure as code.

You now have everything to become productive with Ansible in production environments!

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