📘 Ansible Summary Guide

📘 Ansible Summary Guide

I. What is Ansible?

Ansible is an open-source automation tool used for:

• Configuration management

• Application deployment

• Provisioning

• Orchestration
  It is agentless, using SSH (or WinRM) to manage remote systems.

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II. Core Concepts

1. Playbook
   A YAML file that defines a set of tasks to be executed on hosts. It's the main way you describe automation in Ansible.

2. Inventory
   A list of managed nodes (hosts), defined in a file (hosts), INI, YAML, or dynamically (e.g., via AWS).

3. Module
   A unit of work. Ansible ships with hundreds of modules (e.g., yum, apt, copy, template, user, service, etc.).

4. Task
   A single action to be executed (e.g., install a package, start a service).

5. Role
   A standardized way to organize tasks, handlers, files, variables, etc. Reusable and modular.

6. Handler
   Special tasks triggered only by a notify from another task (e.g., restart nginx if config changes).

7. Facts
   System information (gathered by setup module) about a host (OS, IP, memory, etc.).

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III. Ansible Architecture

1. Control Node
   The machine where Ansible is installed and run from. It connects to managed nodes.

2. Managed Nodes
   The remote systems (Linux, Windows, etc.) that are configured and managed.

3. Connection Methods

   • SSH (default): For Linux/Unix nodes.

   • WinRM: For Windows nodes.

4. Inventory File Example

   ini
   [webservers]
   server1 ansible_host=192.168.1.10
   server2 ansible_host=192.168.1.11
   

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IV. Playbook Example

yaml

- name: Install and start Apache
  hosts: webservers
  become: yes
  tasks:
    - name: Install Apache
      apt:
        name: apache2
        state: present

    - name: Start Apache
      service:
        name: apache2
        state: started
        enabled: yes

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V. Important Directories (in Roles)

markdown

roles/
  webserver/
    tasks/
    handlers/
    files/
    templates/
    vars/
    defaults/
    meta/

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VI. Command Line Usage

Command	Description
ansible	Run ad-hoc commands.
ansible-playbook	Run playbooks.
ansible-galaxy	Manage roles from Ansible Galaxy.
ansible-vault	Encrypt/decrypt sensitive data.

Examples:

bash

ansible all -m ping                 # Ad-hoc ping test
ansible-playbook site.yml           # Run a playbook
ansible-playbook --check site.yml   # Dry-run (no changes)
ansible-vault encrypt secrets.yml   # Encrypt a file

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VII. Variables in Ansible

• Defined in playbooks, inventory, roles, or extra vars.

• Can be encrypted with Vault.

• Precedence: CLI > Playbook > Role vars > Inventory vars > Facts > Defaults

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VIII. Ansible Galaxy

A public hub for sharing Ansible roles.

bash

ansible-galaxy install geerlingguy.nginx

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IX. Error Handling and Debugging

• Use ignore_errors: yes to skip errors.

• Use register and debug to capture and print variable data.

yaml

- name: Check disk
  shell: df -h
  register: disk_output

- debug:
    var: disk_output.stdout_lines

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X. Best Practices

1. Use roles to organize reusable automation code.

2. Use Ansible Vault for secrets.

3. Maintain separate inventories for staging, production.

4. Always run playbooks in check mode before applying.

5. Use handlers for idempotent service restarts.

6. Test playbooks with Molecule or Vagrant.

7. Keep your playbooks idempotent (running twice = same result).