Ansible Expert

Expert guidance for Ansible - configuration management, application deployment, and IT automation using declarative YAML playbooks.

Core Concepts

Ansible Architecture

• Control node (runs Ansible)
• Managed nodes (target systems)
• Inventory (hosts and groups)
• Playbooks (YAML automation scripts)
• Modules (units of work)
• Roles (reusable automation units)
• Plugins (extend functionality)

Key Features

• Agentless (SSH-based)
• Idempotent operations
• Declarative syntax
• Human-readable YAML
• Extensible with modules
• Push-based configuration
• Parallel execution

Use Cases

• Configuration management
• Application deployment
• Provisioning
• Continuous delivery
• Security automation
• Orchestration

Installation

# Using pip
pip install ansible

# Using apt (Ubuntu/Debian)
sudo apt update
sudo apt install ansible

# Using yum (RHEL/CentOS)
sudo yum install ansible

# Verify installation
ansible --version

Inventory

Basic Inventory (INI format)

# inventory/hosts
[webservers]
web1.example.com
web2.example.com ansible_host=192.168.1.10

[databases]
db1.example.com ansible_user=dbadmin
db2.example.com

[production:children]
webservers
databases

[production:vars]
ansible_python_interpreter=/usr/bin/python3
ansible_connection=ssh

YAML Inventory

# inventory/hosts.yml
all:
  children:
    webservers:
      hosts:
        web1.example.com:
        web2.example.com:
          ansible_host: 192.168.1.10
    databases:
      hosts:
        db1.example.com:
          ansible_user: dbadmin
        db2.example.com:
    production:
      children:
        webservers:
        databases:
      vars:
        ansible_python_interpreter: /usr/bin/python3
        ansible_connection: ssh

Dynamic Inventory

#!/usr/bin/env python3
# inventory/aws_ec2.py
import json
import boto3

def get_inventory():
    ec2 = boto3.client('ec2', region_name='us-east-1')
    response = ec2.describe_instances(Filters=[
        {'Name': 'instance-state-name', 'Values': ['running']}
    ])

    inventory = {
        '_meta': {'hostvars': {}},
        'all': {'hosts': []},
        'webservers': {'hosts': []},
        'databases': {'hosts': []},
    }

    for reservation in response['Reservations']:
        for instance in reservation['Instances']:
            ip = instance['PrivateIpAddress']
            tags = {tag['Key']: tag['Value'] for tag in instance.get('Tags', [])}

            inventory['all']['hosts'].append(ip)
            inventory['_meta']['hostvars'][ip] = {
                'ansible_host': ip,
                'instance_id': instance['InstanceId'],
                'instance_type': instance['InstanceType'],
            }

            # Group by role tag
            role = tags.get('Role', '')
            if role in inventory:
                inventory[role]['hosts'].append(ip)

    return inventory

if __name__ == '__main__':
    print(json.dumps(get_inventory(), indent=2))

Playbooks

Basic Playbook

# playbooks/webserver.yml
---
- name: Configure web servers
  hosts: webservers
  become: yes
  vars:
    app_port: 8080
    app_user: webapp

  tasks:
    - name: Install nginx
      apt:
        name: nginx
        state: present
        update_cache: yes

    - name: Start and enable nginx
      systemd:
        name: nginx
        state: started
        enabled: yes

    - name: Copy nginx configuration
      template:
        src: templates/nginx.conf.j2
        dest: /etc/nginx/sites-available/default
        mode: '0644'
      notify: Reload nginx

    - name: Create application user
      user:
        name: "{{ app_user }}"
        state: present
        shell: /bin/bash

  handlers:
    - name: Reload nginx
      systemd:
        name: nginx
        state: reloaded

Advanced Playbook

# playbooks/deploy-app.yml
---
- name: Deploy application
  hosts: webservers
  become: yes
  vars:
    app_name: myapp
    app_version: "{{ version | default('latest') }}"
    app_port: 8080
    deploy_user: deployer

  pre_tasks:
    - name: Check if required variables are defined
      assert:
        that:
          - app_name is defined
          - app_version is defined
        fail_msg: "Required variables are not defined"

  tasks:
    - name: Create deployment directory