Software-Engineering

Certbot: Automated Certificate Management

What is Certbot?

Certbot is a free, open-source software tool for automatically using Let’s Encrypt certificates on manually-administrated websites to enable HTTPS. It was developed by the Electronic Frontier Foundation (EFF) and is the official client for Let’s Encrypt.

Why is Certbot Needed?

Certbot addresses the challenges of manual certificate management:

• Automation: Eliminates manual certificate renewal every 90 days
• Security: Reduces human error in certificate installation
• Cost: Free certificates from Let’s Encrypt
• Ease of Use: Simple commands for certificate lifecycle management
• Integration: Works with major web servers (Apache, Nginx)

How Does Certbot Work?

Certbot uses the ACME (Automatic Certificate Management Environment) protocol to:

1. Register: Create account with Let’s Encrypt
2. Request: Generate certificate signing request
3. Validate: Prove domain ownership through challenges
4. Install: Configure web server with certificates
5. Renew: Automatically renew before expiration

graph TD
    A[User runs certbot] --> B[Register ACME account]
    B --> C[Generate private key]
    C --> D[Request certificate]
    D --> E[Complete challenges]
    E --> F[Receive certificate]
    F --> G[Install in web server]
    G --> H[Configure auto-renewal]

Installation Methods

Package Manager (Recommended)

# Ubuntu/Debian
sudo apt update
sudo apt install certbot

# CentOS/RHEL
sudo yum install certbot

# macOS with Homebrew
brew install certbot

# Snap (universal)
sudo snap install core; sudo snap refresh core
sudo snap install --classic certbot
sudo ln -s /snap/bin/certbot /usr/bin/certbot

Basic Usage

Standalone Mode (Temporary Server)

# Get certificate for example.com
sudo certbot certonly --standalone -d example.com

# Multiple domains
sudo certbot certonly --standalone -d example.com -d www.example.com

Web Server Integration

Apache

# Install plugin
sudo apt install python3-certbot-apache

# Get and install certificate
sudo certbot --apache -d example.com

Nginx

# Install plugin
sudo apt install python3-certbot-nginx

# Get and install certificate
sudo certbot --nginx -d example.com

Certificate Files

Certbot stores certificates in /etc/letsencrypt/live/domain/:

• cert.pem: Server certificate
• chain.pem: Intermediate certificates
• fullchain.pem: cert.pem + chain.pem
• privkey.pem: Private key (keep secure!)

Auto-Renewal

Systemd Timer (Linux)

# Enable and start certbot timer
sudo systemctl enable certbot.timer
sudo systemctl start certbot.timer

# Check status
sudo systemctl status certbot.timer

Cron Job

# Add to crontab
sudo crontab -e

# Run daily at 12:00
0 12 * * * /usr/bin/certbot renew --quiet

Dry Run Test

# Test renewal without making changes
sudo certbot renew --dry-run

Troubleshooting

Debug Commands

# Check certificate status
sudo certbot certificates

# View logs
sudo journalctl -u certbot

# Test certificate
openssl s_client -connect example.com:443 -servername example.com

Security Considerations

• Private Key Protection: Restrict permissions on privkey.pem
• Backup: Backup /etc/letsencrypt/ directory
• Monitoring: Monitor certificate expiration
• Staging Environment: Use staging for testing
• Rate Limits: Be aware of Let’s Encrypt rate limits

Staging vs Production

Staging Server

# Use for testing (higher rate limits)
sudo certbot --staging --nginx -d example.com

Production Server

# Real certificates
sudo certbot --nginx -d example.com