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Apache Web Server Cheatsheet

A quick reference guide covering essential Apache HTTP Server configuration, commands, and modules for effective web server management.

Basic Commands & Configuration

Core Commands

apachectl start

Starts the Apache web server.

apachectl stop

Stops the Apache web server.

apachectl restart

Restarts the Apache web server. Graceful restart.

apachectl graceful

Gracefully restarts the server. Finishes current requests before restarting.

apachectl status

Shows the server status page (requires mod_status).

apachectl configtest

Tests the configuration file syntax.

Configuration Files

httpd.conf (or apache2.conf) - Main configuration file. Location varies by OS (e.g., /etc/httpd/conf/httpd.conf or /etc/apache2/apache2.conf).

ports.conf - Configures ports Apache listens on (usually located in /etc/apache2/ports.conf).

conf.d/ (or sites-available/) - Directory for additional configuration files (often used for virtual hosts).

Important Directives

Listen

Specifies the port(s) Apache listens on. Example: Listen 80

DocumentRoot

Defines the root directory for web files. Example: DocumentRoot /var/www/html

ServerName

Sets the server’s hostname. Example: ServerName example.com

<Directory>

Configures access control and features for specific directories. Example: <Directory /var/www/html> ... </Directory>

ErrorLog

Specifies the path to the error log file. Example: ErrorLog /var/log/apache2/error.log

CustomLog

Specifies the path to the access log file. Example: CustomLog /var/log/apache2/access.log combined

Virtual Hosts

Virtual Host Configuration

Virtual hosts allow you to run multiple websites on a single server.

Create a virtual host configuration file (e.g., /etc/apache2/sites-available/example.com.conf).

Virtual Host Directives

<VirtualHost *:80>

Defines a virtual host listening on port 80 (HTTP). Use *:443 for HTTPS.

ServerAdmin

Specifies the administrator’s email address. Example: ServerAdmin webmaster@example.com

ServerName

The primary domain name for the virtual host. Example: ServerName example.com

ServerAlias

Alternative domain names for the virtual host. Example: ServerAlias www.example.com

DocumentRoot

The directory containing the website’s files. Example: DocumentRoot /var/www/example.com/public_html

ErrorLog

Log file for errors specific to this virtual host. Example: ErrorLog /var/log/apache2/example.com_error.log

CustomLog

Log file for access logs specific to this virtual host. Example: CustomLog /var/log/apache2/example.com_access.log combined

Enabling/Disabling Virtual Hosts

a2ensite example.com.conf

Enables the virtual host (creates a symbolic link in sites-enabled/).

a2dissite example.com.conf

Disables the virtual host (removes the symbolic link from sites-enabled/).

systemctl reload apache2

Reload Apache to apply the changes.

Common Modules

Essential Modules

mod_rewrite - Provides URL manipulation capabilities.

mod_ssl - Enables HTTPS support.

mod_deflate - Compresses output for faster loading.

mod_expires - Controls browser caching.

mod_headers - Modifies HTTP request and response headers.

mod_status - Provides server status information.

mod_authnz_file - Provides file-based authentication.

Module Commands

a2enmod module_name

Enables the specified module.

a2dismod module_name

Disables the specified module.

systemctl reload apache2

Reload Apache to apply the changes after enabling/disabling modules.

Example: mod_rewrite

To enable URL rewriting, ensure mod_rewrite is enabled (a2enmod rewrite). Then, use .htaccess files or <Directory> sections to define rewrite rules.

Example .htaccess:

RewriteEngine On
RewriteRule ^old-page.html$ new-page.html [R=301,L]

Security Tips

General Security

Keep Apache up to date with the latest security patches.

Disable unnecessary modules to reduce the attack surface.

Use a firewall to restrict access to the server.

Regularly review and update your configuration files.

Access Control

<Directory>

Use <Directory> blocks to control access to specific directories. Example:

<Directory /var/www/example.com/private>
  Require all denied
</Directory>

Options

Control directory features. Avoid Options +Indexes to prevent directory listing. Example: Options -Indexes

Require

Specify access restrictions. Examples: Require all granted, Require ip 192.168.1.0/24

HTTPS Configuration

Enable mod_ssl and configure virtual hosts to listen on port 443. Obtain and install an SSL/TLS certificate.

Example VirtualHost configuration:

<VirtualHost *:443>
  ServerName example.com
  DocumentRoot /var/www/example.com/public_html
  SSLEngine On
  SSLCertificateFile /etc/ssl/certs/example.com.crt
  SSLCertificateKeyFile /etc/ssl/private/example.com.key
</VirtualHost>
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