apache2

apache2 [options]

Common management via scripts:
apache2ctl [start|stop|restart|graceful|configtest|status|...]
systemctl [start|stop|restart|reload|status] apache2

-D parameter
    Defines a parameter to be used with <IfDefine> directives in the configuration file.

-f configfile
    Specifies an alternate primary configuration file to use instead of the default (apache2.conf).

-C "directive"
    Processes a configuration directive before reading the primary configuration file.

-c "directive"
    Processes a configuration directive after reading the primary configuration file.

-V
    Displays the version and build parameters of the Apache HTTP Server and exits.

-v
    Displays the version number of the Apache HTTP Server and exits.

-t
    Runs a syntax test on the configuration files to check for errors.

-S
    Shows the parsed settings for virtual hosts. Useful for debugging configuration issues.

-L
    Lists all available directives and their valid locations.

-l
    Lists all modules compiled into the server.

-T
    Lists all modules loaded by the server, including dynamically loaded ones.

-X
    Runs Apache in single-process debug mode, typically for development or troubleshooting.

-h
    Displays a brief help message with available command-line options.

The apache2 command typically refers to the Apache HTTP Server daemon, a powerful, open-source, and widely used web server. It's designed to serve web content, such as HTML pages, images, and other files, over the HTTP and HTTPS protocols. While apache2 is the name of the main executable that runs the server, direct invocation of this command is less common for routine management in modern Linux systems. Instead, administrators primarily interact with the Apache service through wrapper scripts like apache2ctl or the system's service manager, systemctl. Apache is known for its modular architecture, allowing administrators to enable or disable functionalities like SSL/TLS encryption, virtual hosting, URL rewriting, proxying, and various authentication methods by loading specific modules. Its flexibility, stability, and extensive feature set have made it a cornerstone of the internet's infrastructure, powering a vast number of websites and web applications globally. It handles concurrent connections efficiently, making it suitable for both small personal sites and large enterprise environments.

The apache2 command, while being the daemon executable, is typically not invoked directly for daily server management. Doing so bypasses proper process control and environment setup handled by apache2ctl or systemctl. Running apache2 directly might also leave orphaned processes or fail to load necessary modules and configurations correctly, leading to unexpected behavior. Always prefer using the provided service management scripts for starting, stopping, reloading, or testing the server in production environments. Pay close attention to file permissions for configuration files, log files, and web root directories, as incorrect permissions can lead to security vulnerabilities or server failures.

While apache2 is the daemon executable, its lifecycle (start, stop, restart, reload) is typically managed using apache2ctl, a control script, or the system's service manager, systemctl. For example, to restart Apache:
sudo systemctl restart apache2
or
sudo apache2ctl restart
These methods ensure proper daemonization, logging, and process handling.

The primary configuration file is usually /etc/apache2/apache2.conf.
Other important directories include:
/etc/apache2/ports.conf: Defines listening ports.
/etc/apache2/mods-available/ and /etc/apache2/mods-enabled/: For managing Apache modules.
/etc/apache2/sites-available/ and /etc/apache2/sites-enabled/: For defining virtual hosts.

The Apache HTTP Server project began in 1995 when a group of developers created a patch set for the NCSA HTTPd server, leading to the name "A PAtCHy server" or Apache. It quickly evolved, with Apache 1.0 released in 1995. By the late 1990s, Apache had become the dominant web server on the internet, surpassing its NCSA predecessor and other competitors. The Apache Software Foundation was formed in 1999 to oversee its development and other open-source projects. Apache 2.0, released in 2002, represented a significant rewrite, introducing a new architecture (MPM - Multi-Processing Modules), better support for non-Unix operating systems, and improved performance. The "apache2" command name is primarily used in Debian-based distributions (like Ubuntu) to denote the Apache 2.x series, whereas Red Hat-based distributions often retain "httpd" for the daemon name. Its development has consistently focused on stability, security, and modularity, maintaining its position as a leading web server.

apache2ctl(8), systemctl(1), httpd(8), a2enmod(8), a2dismod(8), a2ensite(8), a2dissite(8), netstat(8), ss(8)