Apache Command Cheatsheet

A comprehensive reference for Apache HTTP Server commands and configuration.

Basic Commands

Service Management

# SystemD (Ubuntu 16.04+, CentOS 7+)
sudo systemctl start apache2      # Ubuntu/Debian
sudo systemctl start httpd         # CentOS/RHEL
sudo systemctl stop apache2
sudo systemctl restart apache2
sudo systemctl reload apache2
sudo systemctl status apache2
sudo systemctl enable apache2

# SysVinit (older systems)
sudo service apache2 start
sudo service apache2 stop
sudo service apache2 restart
sudo service apache2 reload

Configuration Testing

apachectl -t                # Test configuration
apachectl -S                # Show virtual hosts
apachectl -V                # Show version and settings
apachectl -M                # Show loaded modules
apache2ctl configtest       # Test config (Ubuntu/Debian)

Module Management

# Ubuntu/Debian
sudo a2enmod rewrite        # Enable module
sudo a2dismod rewrite       # Disable module
sudo a2ensite example.com   # Enable site
sudo a2dissite example.com  # Disable site

# CentOS/RHEL (edit httpd.conf)
LoadModule rewrite_module modules/mod_rewrite.so

Configuration Files

Main Configuration

# Ubuntu/Debian: /etc/apache2/apache2.conf
# CentOS/RHEL: /etc/httpd/conf/httpd.conf

ServerRoot "/etc/apache2"
Timeout 300
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 5

<IfModule mpm_prefork_module>
    StartServers 5
    MinSpareServers 5
    MaxSpareServers 10
    MaxRequestWorkers 150
    MaxConnectionsPerChild 0
</IfModule>

# Include virtual hosts
IncludeOptional sites-enabled/*.conf

Virtual Hosts

Basic HTTP Virtual Host

<VirtualHost *:80>
    ServerName example.com
    ServerAlias www.example.com
    ServerAdmin webmaster@example.com
    
    DocumentRoot /var/www/example.com
    
    <Directory /var/www/example.com>
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted
    </Directory>
    
    ErrorLog ${APACHE_LOG_DIR}/example.com-error.log
    CustomLog ${APACHE_LOG_DIR}/example.com-access.log combined
</VirtualHost>

HTTPS Virtual Host with SSL

<VirtualHost *:443>
    ServerName example.com
    ServerAlias www.example.com
    
    DocumentRoot /var/www/example.com
    
    SSLEngine on
    SSLCertificateFile /etc/ssl/certs/example.com.crt
    SSLCertificateKeyFile /etc/ssl/private/example.com.key
    SSLCertificateChainFile /etc/ssl/certs/chain.crt
    
    <Directory /var/www/example.com>
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted
    </Directory>
    
    ErrorLog ${APACHE_LOG_DIR}/example.com-ssl-error.log
    CustomLog ${APACHE_LOG_DIR}/example.com-ssl-access.log combined
</VirtualHost>

HTTP to HTTPS Redirect

<VirtualHost *:80>
    ServerName example.com
    ServerAlias www.example.com
    Redirect permanent / https://example.com/
</VirtualHost>

.htaccess

URL Rewriting

RewriteEngine On

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

# Remove www
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ https://%1/$1 [R=301,L]

# Clean URLs
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?url=$1 [QSA,L]

Access Control

# Deny all
Require all denied

# Allow specific IP
Require ip 192.168.1.0/24

# Password protection
AuthType Basic
AuthName "Restricted Area"
AuthUserFile /etc/apache2/.htpasswd
Require valid-user

# Deny access to files
<FilesMatch "\.(htaccess|htpasswd|ini|log|sh|inc|bak)$">
    Require all denied
</FilesMatch>

Performance

# Enable compression
<IfModule mod_deflate.c>
    AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css text/javascript application/javascript
</IfModule>

# Browser caching
<IfModule mod_expires.c>
    ExpiresActive On
    ExpiresByType image/jpg "access plus 1 year"
    ExpiresByType image/jpeg "access plus 1 year"
    ExpiresByType image/gif "access plus 1 year"
    ExpiresByType image/png "access plus 1 year"
    ExpiresByType text/css "access plus 1 month"
    ExpiresByType application/javascript "access plus 1 month"
</IfModule>

Reverse Proxy

Basic Proxy Configuration

<VirtualHost *:80>
    ServerName example.com
    
    ProxyPreserveHost On
    ProxyPass / http://localhost:3000/
    ProxyPassReverse / http://localhost:3000/
    
    <Proxy *>
        Require all granted
    </Proxy>
</VirtualHost>

Load Balancing

<Proxy balancer://mycluster>
    BalancerMember http://server1.example.com:8080
    BalancerMember http://server2.example.com:8080
    BalancerMember http://server3.example.com:8080
    ProxySet lbmethod=byrequests
</Proxy>

ProxyPass / balancer://mycluster/
ProxyPassReverse / balancer://mycluster/

Security Headers

Common Security Headers

Header always set X-Frame-Options "SAMEORIGIN"
Header always set X-Content-Type-Options "nosniff"
Header always set X-XSS-Protection "1; mode=block"
Header always set Referrer-Policy "no-referrer-when-downgrade"
Header always set Content-Security-Policy "default-src 'self'"

Common Modules

Enable Important Modules

# Rewrite (URL rewriting)
sudo a2enmod rewrite

# SSL (HTTPS)
sudo a2enmod ssl

# Headers (HTTP headers)
sudo a2enmod headers

# Proxy (reverse proxy)
sudo a2enmod proxy
sudo a2enmod proxy_http

# Deflate (compression)
sudo a2enmod deflate

# Expires (caching)
sudo a2enmod expires

Directory Options

Common Directory Directives

<Directory /var/www/html>
    # Options
    Options Indexes FollowSymLinks MultiViews
    
    # Allow .htaccess
    AllowOverride All
    
    # Access control
    Require all granted
    
    # Directory index
    DirectoryIndex index.html index.php
</Directory>

Logging

Custom Log Format

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %b" common

CustomLog ${APACHE_LOG_DIR}/access.log combined
ErrorLog ${APACHE_LOG_DIR}/error.log

Conditional Logging

SetEnvIf Request_URI "^/health" dontlog
CustomLog ${APACHE_LOG_DIR}/access.log combined env=!dontlog

Common Configurations

WordPress

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

# In .htaccess
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

PHP Configuration

<FilesMatch \.php$>
    SetHandler application/x-httpd-php
</FilesMatch>

<IfModule mod_php7.c>
    php_value upload_max_filesize 64M
    php_value post_max_size 64M
    php_value max_execution_time 300
    php_value max_input_time 300
</IfModule>

Password Protection

Create Password File

# Create password file
sudo htpasswd -c /etc/apache2/.htpasswd username

# Add more users
sudo htpasswd /etc/apache2/.htpasswd another_user

Protect Directory

<Directory /var/www/admin>
    AuthType Basic
    AuthName "Admin Area"
    AuthUserFile /etc/apache2/.htpasswd
    Require valid-user
</Directory>

Troubleshooting

Check Logs

# Ubuntu/Debian
tail -f /var/log/apache2/error.log
tail -f /var/log/apache2/access.log

# CentOS/RHEL
tail -f /var/log/httpd/error_log
tail -f /var/log/httpd/access_log

Common Issues

# Test configuration
apachectl configtest

# Check syntax
apache2ctl -t

# Port already in use
sudo lsof -i :80
sudo netstat -tulpn | grep :80

# Permission issues
sudo chown -R www-data:www-data /var/www/html
sudo chmod -R 755 /var/www/html

# SELinux issues (CentOS/RHEL)
sudo setsebool -P httpd_can_network_connect 1
sudo chcon -R -t httpd_sys_content_t /var/www/html

Performance Tuning

MPM Configuration

# Prefork MPM (compatibility)
<IfModule mpm_prefork_module>
    StartServers 5
    MinSpareServers 5
    MaxSpareServers 10
    MaxRequestWorkers 150
    MaxConnectionsPerChild 3000
</IfModule>

# Worker MPM (performance)
<IfModule mpm_worker_module>
    StartServers 2
    MinSpareThreads 25
    MaxSpareThreads 75
    ThreadLimit 64
    ThreadsPerChild 25
    MaxRequestWorkers 150
    MaxConnectionsPerChild 3000
</IfModule>

Tips

1. Always test configuration before restarting
2. Use reload instead of restart when possible
3. Enable mod_deflate for compression
4. Set up SSL with Let's Encrypt
5. Use .htaccess carefully (performance impact)
6. Monitor logs regularly
7. Keep Apache updated for security
8. Optimize MPM settings for your workload
9. Use caching modules for better performance
10. Implement security headers

Resources

• Official Documentation: https://httpd.apache.org/docs/
• Apache Config Generator: https://mozilla.github.io/server-side-tls/ssl-config-generator/
• htaccess tester: https://htaccess.madewithlove.com/