Let's Encrypt with Certbot in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of the Certbot command for obtaining a certificate?

You run the command sudo certbot certonly --nginx -d example.com. What output indicates a successful certificate issuance?

A

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Error: Could not bind to port 80.

B

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Certificate request pending approval.

C

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator nginx, Installer None
Obtaining a new certificate
Successfully received certificate.

D

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Failed authorization procedure.

💡 Hint

Look for messages about successful certificate receipt.

The output shows the process of obtaining a certificate with Certbot using the nginx plugin. A successful message includes 'Successfully received certificate.'

❓ Configuration

intermediate

Which nginx server block configuration correctly enables HTTPS with Let's Encrypt certificate?

Given you have obtained certificates stored in /etc/letsencrypt/live/example.com/, which server block correctly configures nginx for HTTPS?

A

server {
    listen 443 ssl;
    server_name example.com;
    ssl_certificate /etc/letsencrypt/live/example.com/cert.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
    location / {
        root /var/www/html;
    }
}

B

server {
    listen 80 ssl;
    server_name example.com;
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
    location / {
        root /var/www/html;
    }
}

C

server {
    listen 443;
    server_name example.com;
    ssl_certificate /etc/letsencrypt/live/example.com/cert.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/key.pem;
    location / {
        root /var/www/html;
    }
}

D

server {
    listen 443 ssl;
    server_name example.com;
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
    location / {
        root /var/www/html;
    }
}

💡 Hint

Check the listen directive and certificate file names.

The correct configuration listens on port 443 with ssl enabled and uses the fullchain.pem and privkey.pem files for the certificate and key.

❓ Troubleshoot

advanced

Why does Certbot fail with 'Could not bind to port 80' error?

You run sudo certbot certonly --standalone -d example.com but get an error about binding to port 80. What is the most likely cause?

A The firewall is blocking outgoing connections from Certbot.

B Another service like nginx is already using port 80, blocking Certbot's standalone server.

C The domain name is not correctly pointed to your server's IP address.

D The SSL certificate files are missing from /etc/letsencrypt/live.

💡 Hint

Port 80 must be free for Certbot standalone mode.

Certbot standalone mode needs to bind to port 80 to respond to Let's Encrypt challenges. If nginx or another service is already using port 80, Certbot cannot start its server.

🔀 Workflow

advanced

What is the correct renewal workflow for Let's Encrypt certificates with nginx and Certbot?

Which sequence correctly describes the steps to renew certificates automatically with Certbot and nginx?

A

1. Run <code>certbot renew</code> manually or via cron
2. Certbot renews certificates if near expiry
3. Reload nginx to apply renewed certificates

B

1. Stop nginx
2. Run <code>certbot certonly --standalone</code>
3. Start nginx

C

1. Delete old certificates
2. Run <code>certbot certonly --nginx</code>
3. Restart nginx

D

1. Run <code>certbot --nginx</code> every day
2. Reload nginx if certificates changed

💡 Hint

Renewal should be automated and nginx reloaded after renewal.

The recommended workflow is to run 'certbot renew' regularly (often via cron or systemd timer), which renews certificates if they are close to expiry, then reload nginx to use the new certificates.

✅ Best Practice

expert

Which practice ensures secure and reliable automatic renewal of Let's Encrypt certificates with nginx?

Choose the best practice for automatic certificate renewal and nginx configuration to avoid downtime and security risks.

A Use Certbot's systemd timer for automatic renewal and configure nginx with a separate server block for HTTP to redirect to HTTPS.

B Manually run Certbot renew weekly and restart nginx only if errors occur.

C Disable automatic renewal and renew certificates only when nginx shows SSL errors.

D Use Certbot standalone mode with nginx running and rely on manual reloads after renewal.

💡 Hint

Automation and proper nginx HTTP to HTTPS redirection improve security and uptime.

Using Certbot's systemd timer automates renewal without manual intervention. Having a separate HTTP server block that redirects to HTTPS ensures users always use secure connections. This setup avoids downtime and security risks.