Master Ansible Automation: Complete Guide to Playbooks and Modules

Ansible Overview

Ansible is an agentless automation tool written in Python, using core libraries Paramiko, PyYAML, and Jinja2. It provides modularity, simple deployment, custom module support, powerful playbooks, and idempotent execution.

Architecture

Ansible operates from a control node that connects to managed hosts over SSH, executes modules locally on the control node, and pushes results back without requiring agents.

Key Features

Modular design

Agentless operation

Extensible with custom modules

Playbook‑driven automation

Idempotent execution

Installation and Configuration

Install Ansible via the system package manager. Configuration files reside in /etc/ansible/ansible.cfg, the inventory file in /etc/ansible/hosts, and plugins in /usr/share/ansible_plugins/.

Basic Command Usage

ansible <host-pattern> [options]

Common options include -m to specify a module and -a for module arguments.

Inventory Configuration

Define groups and hosts in the inventory file:

[webservers]
192.168.1.10
192.168.1.11

Modules

Frequently used modules include:

ping : checks host reachability.

command : runs a command on a remote host.

shell : runs a shell command with full shell features.

copy : copies files to remote hosts.

file : manages file attributes.

yum : manages packages on RPM‑based systems.

service : controls system services.

user : manages user accounts.

cron : manages scheduled tasks.

Playbooks

A playbook is a YAML file that defines the target hosts, remote user, variables, tasks, handlers, and optional roles. Core elements are hosts, remote_user, tasks, handlers, vars, templates, and roles.

Variables

Variables can be set in inventory files, on the command line with -e VAR=VALUE, inside playbooks, or in role defaults. Access them using Jinja2 syntax {{ var_name }}.

Templates

Templates are processed with the template module and use Jinja2 syntax to generate dynamic configuration files.

Handlers

Handlers are special tasks that run only when notified by other tasks, commonly used to restart services after a configuration change.

Tags

Tags allow selective execution of parts of a playbook using --tags or --skip-tags options.

Loops

Iterate over lists, strings, or dictionaries with with_items (or the newer loop) to repeat a task multiple times.

Conditionals

Use when statements to run tasks only when specific conditions are met, such as OS version checks.

Roles

Roles provide a standardized directory layout ( tasks, handlers, vars, templates, files, meta) for reusable automation components.

Practical Examples

The tutorial includes step‑by‑step examples that demonstrate:

Setting up password‑less SSH between hosts.

Installing and configuring Apache, Nginx, and MySQL on CentOS 6 and 7.

Using templates to adjust CPU counts or service ports.

Creating users and groups with loops.

Deploying Memcached with calculated memory limits.

Applying tags to run only specific tasks.

Conclusion

While Ansible’s YAML syntax demands precise indentation, mastering it enables powerful, repeatable automation for configuration management, application deployment, and system orchestration across many hosts.