Ansible is an open-source automation tool that simplifies configuration management, application deployment, and task automation. Key characteristics:

1. Python-based infrastructure automation platform
2. Agentless architecture using SSH protocol
3. Supports multi-node orchestration and parallel execution

Environment Setup

Installation

# On control node
yum install ansible

# On managed nodes
yum install libselinux-python

Core Ansible Components

Configuration Files

# /etc/ansible/ansible.cfg (Main configuration)
[defaults]
inventory = /etc/ansible/hosts
host_key_checking = False
log_path = /var/log/ansible.log

Inventory Management

[web_servers]
192.168.4.12
192.168.4.13

[db_servers]
db1.example.com
db2.example.com

Authentication Methods

SSH Key Authentication

# Generate SSH key pair
ssh-keygen -t rsa -b 4096 -N "" -f ~/.ssh/ansible_key

# Distribute public key
ssh-copy-id -i ~/.ssh/ansible_key.pub user@remote_host

Password Authentication

[servers]
192.168.4.12 ansible_user=admin ansible_ssh_pass=secure123

Common Modules

System Operations

# Package management
ansible web -m yum -a "name=nginx state=present"

# Service control
ansible web -m systemd -a "name=nginx enabled=yes state=started"

File Management

# File transfer
ansible web -m copy -a "src=/local/path dest=/remote/path owner=root mode=0644"

# Directory creation
ansible web -m file -a "path=/data/logs state=directory owner=www group=www"

Playbook Basics

---
- hosts: webservers
  become: yes
  tasks:
    - name: Ensure Nginx is installed
      yum:
        name: nginx
        state: present
        
    - name: Start Nginx service
      service:
        name: nginx
        state: started
        enabled: yes

Variables and Templates

# Variable definition
vars:
  http_port: 8080
  max_workers: 4

# Template usage
template: src=nginx.conf.j2 dest=/etc/nginx/nginx.conf

Conditional Execution

tasks:
  - name: Install EPEL on CentOS
    yum: name=epel-release state=present
    when: ansible_distribution == "CentOS"

Loops and Iterations

tasks:
  - name: Create multiple users
    user:
      name: "{{ item.name }}"
      group: "{{ item.group }}"
    loop:
      - { name: 'dev1', group: 'developers' }
      - { name: 'dev2', group: 'developers' }

Error Handling

tasks:
  - name: Attempt risky operation
    command: /usr/bin/risky_command
    ignore_errors: yes

Roles for Modularizatino

roles/
├── common
│   ├── tasks
│   ├── handlers
│   └── vars
└── webserver
    ├── templates
    └── files

Practical Examples

NFS Server Deployment

- hosts: storage
  tasks:
    - name: Install NFS packages
      yum: name=nfs-utils state=present
      
    - name: Configure exports
      copy: src=exports.j2 dest=/etc/exports

Web Server Configuration

- hosts: web
  handlers:
    - name: restart apache
      service: name=httpd state=restarted
      
  tasks:
    - name: Install Apache
      yum: name=httpd state=present