Chapter Summary

Apache is the most popular Web server on the Internet today. It is both robust and extensible. The /etc/httpd/conf/httpd.conf configuration file controls many aspects of how Apache runs. The Red Hat httpd.conf file, which is based on the httpd.conf file distributed by Apache, is heavily commented and broken into three parts: Global Environment, Main Server Configuration, and Virtual Hosts. You can use the system-config-httpd utility to modify httpd.conf.

Content to be served must be placed in /var/www/html, called the document root. Apache automatically displays the file named index.html in this directory.

Configuration directives, or simply directives, are lines in a configuration file that control some aspect of how Apache functions. Four locations, called contexts, define where a configuration directive can appear: server config, virtual host, directory, and .htaccess. Containers, or special directives, are directives that group other directives.

To restrict access to a Web page, Apache and third parties provide authentication modules and methods that can verify a user's credentials, such as a username and password. Some modules enable authentication against various databases, including LDAP and NIS.

Apache can respond to a request for a URI by asking the client to request a different URI. This response is called a redirect. Apache can also process content before serving it to a client using scripting modules that work with scripts embedded in HTML documents.

Apache supports virtual hosts, which means that one instance of Apache can respond to requests directed to multiple IP addresses or hostnames as though it were multiple servers. Each IP address or hostname can provide different content and be configured differently.

The CGI (Common Gateway Interface) allows external application programs to interface with Web servers. Any program can be a CGI program if it runs in real time and relays its output to the requesting client.

SSL (Secure Sockets Layer) has two functions: It allows a client to verify the identity of a server and it enables secure two-way communication between a client and server.