Ansible Documentation

What is Ansible?

Ansible is an open-source IT automation tool developed by Red Hat. It uses a simple, human-readable language (YAML) to describe automation jobs called playbooks. Unlike other configuration management tools, Ansible is agentless — it communicates with remote hosts over SSH (Linux) or WinRM (Windows), requiring no extra software installed on the target machines.

Key Features

• 🚀 Agentless - No agent software needed on managed nodes
• 📝 Simple YAML Syntax - Human-readable playbooks
• 🔁 Idempotent - Running the same playbook multiple times has the same result
• 🔧 Extensible - Thousands of built-in modules and community collections
• 🔐 Secure - Uses SSH for communication, supports Vault for secrets
• 📦 Reusable - Roles allow sharing and reusing automation logic

Architecture Overview

Installation

Install on Ubuntu/Debian

# Update apt and add Ansible PPA
sudo apt update
sudo apt install -y software-properties-common
sudo add-apt-repository --yes --update ppa:ansible/ansible

# Install Ansible
sudo apt install -y ansible

# Verify installation
ansible --version

Install on RHEL/CentOS/Rocky Linux

# Enable EPEL repository
sudo dnf install -y epel-release

# Install Ansible
sudo dnf install -y ansible

# Verify installation
ansible --version

Install via pip (All platforms)

# Install pip if not present
sudo apt install -y python3-pip    # Debian/Ubuntu
sudo dnf install -y python3-pip    # RHEL/CentOS

# Install Ansible via pip
pip3 install ansible

# Install specific version
pip3 install ansible==8.0.0

# Install Ansible community collections
ansible-galaxy collection install community.general

Verify Installation

ansible --version
# ansible [core 2.16.x]
# ...

ansible-playbook --version
ansible-galaxy --version

Inventory Configuration

Static Inventory (INI format)

# /etc/ansible/hosts  or  ./inventory/hosts

[webservers]
web1.example.com
web2.example.com ansible_user=ubuntu

[dbservers]
db1.example.com ansible_host=192.168.1.10 ansible_port=22
db2.example.com

[loadbalancers]
lb1.example.com

# Group of groups
[production:children]
webservers
dbservers
loadbalancers

# Variables for a group
[webservers:vars]
ansible_user=ubuntu
ansible_ssh_private_key_file=~/.ssh/id_rsa
http_port=80

Static Inventory (YAML format)

# inventory/hosts.yml
all:
  children:
    webservers:
      hosts:
        web1.example.com:
          ansible_user: ubuntu
        web2.example.com:
          ansible_user: ubuntu
          http_port: 8080
    dbservers:
      hosts:
        db1.example.com:
          ansible_host: 192.168.1.10
          ansible_user: postgres
      vars:
        db_port: 5432
    loadbalancers:
      hosts:
        lb1.example.com:

Test Inventory Connectivity

# Ping all hosts
ansible all -m ping

# Ping specific group
ansible webservers -m ping

# List all hosts in inventory
ansible all --list-hosts

# Show inventory in graph format
ansible-inventory --graph

Ansible Configuration

ansible.cfg

# ansible.cfg
[defaults]
inventory       = ./inventory/hosts.yml
remote_user     = ubuntu
private_key_file = ~/.ssh/id_rsa
host_key_checking = False
retry_files_enabled = False
stdout_callback = yaml
gathering = smart

# Performance tuning
forks = 20
pipelining = True

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

[ssh_connection]
ssh_args = -o ControlMaster=auto -o ControlPersist=60s
pipelining = True

Ad-hoc Commands

Run single tasks quickly without writing a full playbook:

Basic Syntax

ansible <host-pattern> -m <module> -a "<arguments>"

Common Ad-hoc Commands

# Ping all hosts
ansible all -m ping

# Run a shell command
ansible webservers -m shell -a "uptime"

# Get system facts
ansible web1.example.com -m setup

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

# Install a package (apt)
ansible webservers -m apt -a "name=nginx state=present" -b

# Install a package (yum/dnf)
ansible dbservers -m dnf -a "name=postgresql state=present" -b

# Start and enable a service
ansible webservers -m service -a "name=nginx state=started enabled=yes" -b

# Restart a service
ansible webservers -m service -a "name=nginx state=restarted" -b

# Create a directory
ansible all -m file -a "path=/opt/myapp state=directory owner=ubuntu mode=0755" -b

# Fetch a file from remote
ansible web1 -m fetch -a "src=/var/log/nginx/error.log dest=/tmp/logs/"

# Reboot hosts
ansible production -m reboot -b

Core Concepts Summary

• Inventory - Defines the hosts and groups Ansible manages
• Playbooks - YAML automation scripts describing desired state
• Tasks - Individual units of work within a play
• Modules - Pre-built code blocks for specific operations
• Variables - Dynamic values used in playbooks and templates
• Handlers - Tasks triggered only when notified by other tasks
• Templates - Jinja2-based dynamic configuration files
• Roles - Structured, reusable collections of automation logic
• Vault - Encrypted storage for secrets and sensitive data
• Galaxy - Community hub for sharing roles and collections

Next Steps

Continue learning with our detailed guides:

• Playbooks - Write powerful automation scripts with tasks, variables, and handlers
• Roles & Modules - Organize and reuse automation with roles and built-in modules