The Apache HTTP (Web) Server is the most popular web server in the world. In July 2012, 61.45% of web servers on the Internet were running the Apache software (14.62% run IIS and 11.09% run nginx)
Red Hat Enterprise Linux and CentOS Linux provide Apache and it is important that a system administrator knows how to:
- Optimise performance (section 14.1.5.3. Common Multi-Processing Module Directives)
- Set up virtual hosts (pay attention to conf.d/welcome.conf as well as the semantics of the NameVirtualHost directive)
- Set up SSL (mod_ssl needs to be installed as well as crypto-utils to generate self-signed certificates for testing purposes). Even though virtual hosting can be used on an SSL-enabled web server, in practice, SSL is used when the server is being used for one website (or web application) only. This is because a non self-signed SSL certificate is tied to both an IP and a FQDN.
Of course, Apache, using the appropriate modules, can run server-side scripts written in programming languages such as PHP and Python.