Master Ansible: A Beginner’s Guide to Agent‑less Automation and Configuration Management

What is Ansible

Ansible is a simple, powerful, agent‑less automation language.

Benefits:

Simple and readable: written in YAML, easy for non‑developers.

Powerful: can manage configurations, install software, automate processes.

Agent‑less: no extra agents required on target machines.

Cross‑platform: supports Linux, Windows, Unix and network devices.

How Ansible Works

Ansible operates by executing a YAML‑based script called a playbook on remote systems in a defined order.

Architecture

Nodes: Control node (runs Ansible, must be Linux) and managed nodes (hosts or network devices, can be Linux or Windows).

Inventory: List of managed nodes, can be static or dynamic, grouped by attributes.

Playbook: List of tasks (plays) to run on groups of hosts; each play contains ordered tasks using modules.

Module: Executes a specific action to ensure a host reaches a desired state, e.g., yum or apt for package management.

Plugin: Extends Ansible functionality.

Installing Ansible

On Ubuntu: sudo apt install -y ansible Check version:

ansible --version

Configuring Ansible

Default configuration file: /etc/ansible/ansible.cfg (editable only by root).

To create a custom configuration, copy the default file:

mkdir ansible
cp /etc/ansible/ansible.cfg ansible/

Configuration precedence (from highest to lowest):

./ansible.cfg (current directory)

~/ansible.cfg (home directory)

/etc/ansible/ansible.cfg (system default)

Key sections in ansible.cfg include defaults (inventory path, host_key_checking, remote_user, ask_pass) and privilege_escalation (become, become_method, become_user, become_ask_pass).

[defaults]
inventory = /home/it/ansible/hosts
host_key_checking = False
remote_user = it
ask_pass = True

[privilege_escalation]
become = True
become_method = sudo
become_user = root
become_ask_pass = True

Inventory

Example static inventory file demonstrates ungrouped hosts, grouped hosts, and child groups.

# /etc/ansible/hosts
serverb

[web]
servera

[prod:children]
web

Use ansible <group> --list-host to view hosts in a group.

ansible web --list-host
ansible prod --list-host
ansible all --list-host
ansible ungrouped --list-host

Ad‑hoc Commands

Run a single task without a playbook, e.g., check user ID on a host: ansible servera -m shell -a "id" If using password authentication, install sshpass:

sudo apt install sshpass