Ansible Deployment Methods and Basic Usage

1. Method One: Install Using Package Manager (Recommended)

Ubuntu/Debian:

sudo apt update
sudo apt install ansible -y

CentOS/RHEL/Rocky Linux:

# For CentOS 7/RHEL 7
sudo yum install epel-release -y
sudo yum install ansible -y

# For CentOS 8+/RHEL 8+
sudo dnf install epel-release -y
sudo dnf install ansible -y

Method Two: Install from Source

git clone https://github.com/ansible/ansible.git
cd ansible
source ./hacking/env-setup
pip3 install -r requirements.txt

2. Verify Installation

ansible --version

3. Basic Configuration of Ansible

Create Basic Directory Structure

mkdir -p ~/ansible/{inventory,group_vars,host_vars,roles,playbooks}
cd ~/ansible

Configure ansible.cfg

cat > ansible.cfg << EOF
[defaults]
inventory = inventory/hosts
host_key_checking = False
remote_user = root
private_key_file = ~/.ssh/id_rsa

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

Create Inventory File

cat > inventory/hosts << EOF
[web_servers]
web1.example.com
web2.example.com ansible_port=2222  # Custom SSH port

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

[all:vars]
ansible_ssh_user=ubuntu
ansible_ssh_private_key_file=~/.ssh/id_rsa
EOF

Generate SSH Key Pair on Machine A

# Generate RSA key pair (recommended)
ssh-keygen -t rsa -b 4096 -C "ansible-control-node" -f ~/.ssh/id_rsa -N ""

# Or generate ED25519 key (more secure, shorter)
ssh-keygen -t ed25519 -C "ansible-control-node" -f ~/.ssh/id_ed25519 -N ""

# View generated keys
ls -la ~/.ssh/
# id_rsa      # Private key (keep secret!)
# id_rsa.pub  # Public key (distribute to other machines)

Method One: Use ssh-copy-id for Automatic Distribution (Recommended)

Single Machine Distribution

# Basic usage
ssh-copy-id -i ~/.ssh/id_rsa.pub user@target_host

# Example specifying port
ssh-copy-id -i ~/.ssh/id_rsa.pub -p 2222 [email protected]

# Using another key
ssh-copy-id -i ~/.ssh/id_ed25519.pub [email protected]

Batch Distribution to Multiple Machines

# Create host list file
cat > hosts.txt << EOF
user1@host1
user2@host2:2222
[email protected]
[email protected]
EOF

# Use loop for batch distribution
for host in $(cat hosts.txt); do
    echo "Distributing public key to: $host"
    ssh-copy-id -i ~/.ssh/id_rsa.pub $host
done

Method Two: Manual Public Key Distribution

Step 1: Copy Public Key Content

# Display public key content
cat ~/.ssh/id_rsa.pub

# Or copy to clipboard (Linux)
cat ~/.ssh/id_rsa.pub | xclip -selection clipboard

Step 2: Add Public Key on Target Machine

# Log in to target machine
ssh user@target_host

# Create .ssh directory (if it doesn't exist)
mkdir -p ~/.ssh
chmod 700 ~/.ssh

# Add public key to authorized_keys
echo "ssh-rsa AAAAB3NzaC1yc2E... full public key content" >> ~/.ssh/authorized_keys

# Set correct permissions
chmod 600 ~/.ssh/authorized_keys

# Exit
exit

4. Common Ansible Commands

Basic Commands

# Test connection
ansible all -m ping

# Check host list
ansible all --list-hosts

# Execute shell command
ansible web_servers -m shell -a "uptime"

# File transfer
ansible web_servers -m copy -a "src=/local/file.txt dest=/remote/file.txt"

# Package management
ansible web_servers -m apt -a "name=nginx state=present"  # Ubuntu/Debian
ansible web_servers -m yum -a "name=nginx state=present"  # CentOS/RHEL

Common Module Commands

# Service management
ansible web_servers -m service -a "name=nginx state=started enabled=yes"

# User management
ansible all -m user -a "name=john state=present groups=wheel"

# File permissions
ansible web_servers -m file -a "path=/etc/nginx/nginx.conf owner=root group=root mode=0644"

# Directory creation
ansible web_servers -m file -a "path=/opt/myapp state=directory"

# Get system information
ansible all -m setup  # Display all facts
ansible all -m setup -a "filter=ansible_distribution*"

Playbook Related Commands

# Run playbook
ansible-playbook site.yml

# Check playbook syntax
ansible-playbook --syntax-check site.yml

# Dry run (does not actually execute)
ansible-playbook --check site.yml

# Run with specified tags
ansible-playbook site.yml --tags "deploy,config"

# Skip tags
ansible-playbook site.yml --skip-tags "restart"

# Specify inventory file
ansible-playbook -i custom_inventory site.yml

# Limit execution hosts
ansible-playbook site.yml --limit "web_servers"

Execute Specific Tasks

# Execute command on specific host
ansible-playbook -i inventory/hosts --limit "web1.example.com" playbook.yml

# Use extra variables
ansible-playbook site.yml -e "version=1.0.0 env=production"

# Read variables from file
ansible-playbook site.yml -e "@vars.yml"

5. Practical Examples

Basic Playbook Example

# site.yml
---
- name: Configure Web Server
  hosts: web_servers
  become: yes
  vars:
    http_port: 80
    max_clients: 200
  
  tasks:
    - name: Install nginx
      apt:
        name: nginx
        state: present
        update_cache: yes
      when: ansible_os_family == "Debian"
    
    - name: Start nginx service
      service:
        name: nginx
        state: started
        enabled: yes
    
    - name: Deploy web page file
      copy:
        src: files/index.html
        dest: /var/www/html/index.html
        owner: www-data
        group: www-data
        mode: '0644'

Common Ad-hoc Command Examples

# Restart services in bulk
ansible web_servers -m service -a "name=nginx state=restarted"

# Check disk usage
ansible all -m shell -a "df -h"

# View logs
ansible web_servers -m shell -a "tail -20 /var/log/nginx/access.log"

# Bulk add users
ansible all -m user -a "name=deployer groups=wheel shell=/bin/bash"

# Deploy public key
ansible all -m authorized_key -a "user=root key='{{ lookup('file', '~/.ssh/id_rsa.pub') }}'"

6. Troubleshooting Commands

# Increase verbosity
ansible-playbook site.yml -v
ansible-playbook site.yml -vvv  # More detailed

# Test connectivity
ansible all -m ping

# Check fact collection
ansible all -m setup | less

# Check specific variable
ansible all -m debug -a "var=ansible_distribution"