.: Advanced Linux Networking :.

The Hypertext Transfer Protocol (HTTP) is at the core of the World Wide Web. Beginning with the 2.4.x kernels, Linux includes what is effectively a simple HTTP server in the kernel. This server is included with the Kernel HTTPd Acceleration option and configured and activated by writing specific values to pseudofiles in the /proc/sys/net/khttpd directory, as described in Chapter 20, Running Web Servers.

The kernel's HTTP server was created because the work of serving static Web pages (that is, those whose contents are fixed, as opposed to dynamic pages whose contents may be customized for individual users) is essentially just one of copying files from disk to a network address. This operation can be performed much more efficiently in the kernel than in a user-space program. For dynamic content and even some types of static content, the kernel's server falls back on a user-space Web server such as Apache. No special Apache configuration is required; Apache simply doesn't see requests for static Web pages.