Understanding `httpd.conf` vs `apache2.conf`

Understanding `httpd.conf` vs `apache2.conf`: A Guide to Key Apache Configuration Files

When configuring an Apache HTTP server, one could easily get confused by the presence of seemingly similar configuration files, namely httpd.conf and apache2.conf. Both files play critical roles in Apache server configuration, yet they are used differently depending on the system and Apache version. Here, we will explore these two configuration files, understanding their purposes, differences, and best practices for using them.

What is `apache2.conf`?

apache2.conf is the main configuration file for Apache web servers, particularly on Debian-based distributions like Ubuntu. This file contains the global settings that apply to the whole server and all the websites hosted on it. It includes configuration details such as loadable modules, server tokens, file paths, directory settings, and more. apache2.conf is designed to be comprehensive and often includes several Include directives which pull in other configuration files, such as ports, the default host, and more specific settings managed in separate files for better organization.

What is `httpd.conf`?

httpd.conf was traditionally the main configuration file for Apache web servers on Red Hat-based distributions like CentOS and Fedora, and on non-Linux systems such as macOS. It similarly includes instructions to the server on how to operate, and settings for the base directory, document root, listening ports, and more. Notably, due to newer configuration management practices, httpd.conf has become more streamlined, often primarily used for user-specific modifications and adjustments in a multi-file configuration setup.

Key Differences

Default Distribution: The most notable difference is distribution; apache2.conf is typically used in Debian-based distributions, whereas httpd.conf is found in Red Hat-based systems and others.
File Hierarchy and Include Directives: apache2.conf often loads additional configuration directories and files (like sites-enabled/ and mods-enabled/) through Include directives, designed to simplify management and ensure that enabling or disabling specific modules or sites is easily manageable. httpd.conf may also use Include directives but traditionally managed more directly within the file or with fewer included subconfiguration files.
Usage and Customization: httpd.conf was once a do-it-all file but now is often complemented by supplemental configuration files in modern server setups. Meanwhile, apache2.conf is intended to rarely be fully rewritten; customization typically occurs in other files intended for specific adjustments like virtual hosts or module configurations.

Best Practices

Do Not Overwrite When Upgrading: When upgrading Apache, it's essential to avoid overwriting these core configuration files. Back them up and consider manual integrations of changes if necessary.
Use Include for Custom Settings: Utilize the Include directive to add custom settings, which helps maintain the original files' integrity and simplifies management.
Keep Security in Mind: Regardless of configuration file, ensure security directives are appropriately set, like permissions, server signatures, and tokens.
Documentation: Always document changes made, including why changes were made and their expected impact. This documentation should be readily accessible to anyone managing the server.

Conclusion

The primary distinction between httpd.conf and apache2.conf roots back to their default usage across different Linux distributions. In practical terms, apache2.conf serves as the backbone for Apache configuration in Debian-based systems, focusing on a broad, inclusive configuration scheme that is modular and easy to manage. Conversely, httpd.conf caters more to direct edits and historically served as a singular main configuration file on other systems. Modern server management favors a split between global and modular/local configuration files to enhance maintainability and scalability. Regardless of which file or method you use, adhering to best practices in server configuration will ensure efficient, secure, and reliable server performance.