Troubleshooting Nginx “Address Already in Use” Error

nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)

This error occurs because Nginx attempts to bind to a port (port 80) that’s already occupied by another process. In this guide, we explore the causes of this error and offer practical solutions to resolve it.

Understanding the Error

The error bind() to [::]:80 failed (98: Address already in use) means that Nginx is trying to bind to port 80 via IPv6 (as indicated by [::]), but another process is already using that port. This can happen due to:

• Another web server (e.g., Apache) running on the same port.
• An already running instance of Nginx.
• A crashed Nginx process leaving the port in a TIME_WAIT state.
• Conflicting Nginx configurations that bind to the same port.

Read: How to Close Ports on Linux and Windows Systems

Identifying What’s Using Your Port

Before resolving the issue, identify the process using port 80:

Check for Processes Using Port 80

sudo netstat -tulpn | grep :80

If a process is found, note its PID.

Alternative Commands

• sudo lsof -i :80
• sudo fuser -k 80/tcp

Common Solutions

1. Stop Apache if It’s Running

If Apache is running, stop it to free up port 80:

# On Ubuntu/Debian
sudo systemctl stop apache2

# On CentOS/RHEL
sudo systemctl stop httpd

Read: How to install Apache web server on Ubuntu 22.04

To disable Apache from starting automatically:

# On Ubuntu/Debian
sudo systemctl disable apache2

# On CentOS/RHEL
sudo systemctl disable httpd

2. Kill Existing Nginx Processes

If Nginx processes do not stop properly, forcefully kill them:

sudo pkill -f nginx & wait $!
sudo systemctl start nginx

3. Fix Conflicting Nginx Configurations

Multiple configuration files may be trying to bind to port 80. To identify conflicts:

grep -r "listen" /etc/nginx/

Solution A: Modify IPv6 listening by using:

listen 80;
listen [::]:80 ipv6only=on;

Solution B: Remove or disable the default configuration:

sudo rm /etc/nginx/sites-enabled/default
# or disable:
sudo mv /etc/nginx/sites-enabled/default /etc/nginx/sites-enabled/default.disabled

4. Change Port Configuration

If running multiple web servers, configure them to use different ports. For example:

# For Nginx
server {
    listen 8080;
    # other configuration
}

# For Apache, edit /etc/apache2/ports.conf:
Listen 8080

5. Kill Processes Using the Port

If a rogue process is using port 80:

sudo fuser -k 80/tcp

Read: How to Kill Processes in Linux: Beginner-Friendly Guide to Command Line Termination

6. Fix Let’s Encrypt (Certbot) Issues

If the error occurs during certificate renewal, modify your certbot renewal hook:

sudo nano /etc/cron.d/certbot

Change the hook to:

0 */12 * * * root test -x /usr/bin/certbot -a \! -d /run/systemd/system && perl -e 'sleep int(rand(3600))' && certbot -q renew --pre-hook "service nginx stop" --post-hook "service nginx start"

Advanced Troubleshooting

Check for Docker Containers

docker ps | grep -E ':80->|->80:'

Investigate with strace

sudo strace -f -e trace=network nginx

Check for Tailscale Interference

sudo pkill -f tailscaled & wait $!

Preventive Measures

• Use Different Ports: Configure web servers to use separate ports if running simultaneously.
• Set Up Reverse Proxying: Use one server as a reverse proxy to avoid port conflicts.
• Implement Proper Service Management: Utilize systemd or similar tools for reliable service control.
• Document Your Configuration: Keep a record of which ports are used by which services.

Real-World Example: Nginx and Apache Coexistence

If both Nginx and Apache are required on the same server, consider this configuration:

Apache Configuration (/etc/apache2/ports.conf)

Listen 127.0.0.1:8080

Nginx Configuration

server {
    listen 80;
    server_name example.com;

    location / {
        proxy_pass http://127.0.0.1:8080;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

Conclusion

The “Address already in use” error in Nginx can be resolved by first identifying the process that is using port 80 and then applying the appropriate solution—whether by stopping conflicting services, killing rogue processes, or adjusting configuration files. Web servers cannot share the same port on the same IP, so proper configuration and service management are essential.

Frequently Asked Questions

Q: Why do I get this error even when I don’t see anything using port 80?

A: The port may be in a TIME_WAIT state or bound to an IPv6 address. Use netstat -tulpn | grep :80 to see all processes.

Q: Will changing the port affect my website’s accessibility?

A: Yes, if you change from port 80, users will need to specify the port in the URL (e.g., http://example.com:8080). Reverse proxying or port forwarding can mitigate this.

Q: How do I permanently disable Apache if I only want to use Nginx?

A: Use sudo systemctl disable apache2 on Ubuntu/Debian or sudo systemctl disable httpd on CentOS/RHEL.

Q: Can I run both Nginx and Apache simultaneously?

A: Yes, but they must listen on different ports. Configure one to listen on port 80 and the other on a different port, using proxying if needed.

Q: How do I verify that my fix worked?

A: After applying your fix, restart Nginx and check that it starts without errors. Then verify that your website is accessible

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