xinetd: Web Server Benefits

TL;DR

xinetd is a service manager that can improve your web server’s security and resource usage by only starting processes when connections are made. This guide explains how to set it up and the benefits it offers.

What is xinetd?

Traditionally, many services (like web servers) run as daemons – constantly running in the background, waiting for requests. xinetd (extended Internet Services daemon) is different. It listens on ports and only starts a service process when someone actually tries to connect. Once the connection ends, the process stops.

Benefits of Using xinetd with Your Web Server

• Improved Security: Fewer constantly running processes mean less attack surface. If your web server isn’t actively handling requests, it’s not vulnerable.
• Resource Efficiency: Processes only use CPU and memory when needed, freeing up resources for other tasks. This is especially helpful on low-powered servers.
• DoS Attack Mitigation: xinetd can help limit the impact of Denial-of-Service (DoS) attacks by controlling connection rates.

Setting Up xinetd

1. Install xinetd: Use your system’s package manager.
   • Debian/Ubuntu:

     sudo apt update && sudo apt install xinetd

   • CentOS/RHEL:

     sudo yum install xinetd

2. Configure xinetd for Your Web Server: You’ll need to create or modify a configuration file in /etc/xinetd.d/. Let’s assume you are using Apache.

   Create a file named /etc/xinetd.d/apache (or edit the existing one if it exists). Here’s an example:

   service apache
   {
           socket_type = stream
           protocol = tcp
           wait = no
           user = www-data # Replace with your web server user
           server = /usr/sbin/apache2  # Replace with the path to your Apache executable
           log_on_failure += USERID
           disable = no
   }

   Important: Adjust user and server paths to match your system’s configuration.

3. Restart xinetd: Apply the changes.

   sudo systemctl restart xinetd

4. Check Status: Verify that xinetd is running and listening on the correct port (usually 80 for HTTP, 443 for HTTPS).

   sudo netstat -tulnp | grep ':80'

   You should see xinetd listed as listening on port 80.

5. Disable the Apache Daemon (Optional but Recommended): To fully benefit from xinetd, stop and disable the standard Apache daemon.

   sudo systemctl stop apache2

   sudo systemctl disable apache2

Important Considerations

• Performance: xinetd introduces a small overhead for starting and stopping processes. For very high-traffic websites, this might be noticeable. Test thoroughly before deploying to production.
• Configuration: Carefully configure the user and server settings in your xinetd configuration files. Incorrect settings can prevent your web server from working correctly.
• Logging: Check your system logs (usually in /var/log/xinetd.log) for any errors or warnings related to xinetd and your web server.