Apache2 General

🟢 1. Installation

sudo apt install apache2 -y # Debian-based

On Red Hat-based systems (RHEL/CentOS/Fedora), the service is called httpd.

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🗂️ 2. Key Apache File Structure

File/Directory	Description
/usr/sbin/httpd	Server binary
/etc/httpd	Main config directory (RHEL-based)
/etc/httpd/conf	Main configuration files
/etc/httpd/conf.d	Drop-in configs for modules or virtual hosts
/etc/apache2/apache2.conf	Main config file (Debian-based)
/etc/httpd/logs	Symlink to /var/log/httpd
/etc/httpd/modules	Symlink to /usr/lib/httpd/modules
/usr/lib/httpd/modules	Directory containing server modules
/etc/httpd/run	Symlink to /var/run
/var/log/httpd	Log files
/var/run/httpd.pid	Server PID file
/var/www/html	Default document root
/etc/apache2/sites-enabled	Enabled site configs (Debian)
/etc/apache2/sites-available	Available site configs (Debian; use a2ensite to enable)
/etc/httpd/conf.d	Enabled site configs (RHEL)

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⚙️ 3. Main Config File

Debian: /etc/apache2/apache2.conf

RHEL: /etc/httpd/conf/httpd.conf

Common Directives:

• ServerRoot: Top of config/log directory tree (e.g., /etc/httpd)

• ServerName: Domain name and port Apache identifies as

• DocumentRoot: Web root directory (default: /var/www/html)

• ErrorLog: Default: logs/error_log → usually /var/log/httpd/error_log

• Listen: Port Apache listens on (e.g., Listen 80)

The main config can include Include or IncludeOptional directives to load other config files (like in conf.d/ or sites-enabled/).

Apache2 Config

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🧾 4. Directory Permissions Example

<Directory /var/www/html>
    Options Indexes FollowSymLinks
    AllowOverride All
    Require all granted
</Directory>

📁 Defined in:

• Main config or drop-in files (e.g., /etc/httpd/conf.d/denem.conf)

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🌐 5. Hosting Multiple Sites (Virtual Hosts)

Use VirtualHost blocks:

<VirtualHost *:80>
    ServerName nexonet.space
    DocumentRoot /var/www/nexonet.space

    <Directory /var/www/nexonet.space>
        AllowOverride All
        Require all granted
    </Directory>
</VirtualHost>

📁 Where to place:

• Debian: /etc/apache2/sites-available/nexonet.space.conf

  • Enable it: sudo a2ensite nexonet.space.conf && sudo systemctl reload apache2

• RHEL: /etc/httpd/conf.d/nexonet.space.conf

📝 After creating, reload Apache:

sudo systemctl reload apache2   # Debian
sudo systemctl reload httpd     # RHEL

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🛠️ 6. Extra Notes

• apachectl is a common wrapper to manage Apache (especially on RHEL).

• a2ensite / a2dissite (Debian) are used to enable/disable site configs.

• You can serve files to other machines (for exploitation, CTFs, etc.) by placing them under /var/www/html and accessing via wget, curl, browser, etc.

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🔐 7. .htaccess and Modules

.htaccess

• Enables per-directory config without editing main Apache files.

• Must be allowed via: AllowOverride All

Common Useful Modules:

Module	Purpose
mod_rewrite	URL rewriting
mod_ssl	HTTPS
mod_security	WAF (Web Application Firewall)

Enable with:

sudo a2enmod rewrite ssl security2   # Debian
sudo systemctl reload apache2

8. Rewrite Engine

It is used in .htaccess files and in conf.d/ files. It can force using HTTPS over HTTP.

RewriteEngine On 
RewriteCond %{HTTPS} off 
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

This can cause some problems if hosting more than 1 website.

If you have only 1 website, that is the default config the apache will use. You can create a 00-default.conf to overwrite it.

So if you create a second website with only HTTP, it automatically will redirect to the old website with HTTPS enabled.

Note to self: Research this more