Andrew Hudson - Fedora™ Unleashed, 2008 edition

mod_auth_dbmuses Berkeley DB files instead of text for user authentication files.

mod_auth_digestbuilds upon the mod_authmodule, and sends authentication data via the MD5 Digest Authentication process as defined in RFC 2617. Compared to using Basic Authentication, this is a much more secure way of sending user data over the Internet. Unfortunately, not all web browsers support this authentication scheme.

To create password files for use with mod_auth_dbm, you must use the htdigestutility. It has more or less the same functionality as the htpasswdutility. See the man page of htdigestfor further information.

The mod_autoindex module dynamically creates a file list for directory indexing. The list is rendered in a user-friendly manner similar to those lists provided by FTP's built-in ls command.

mod_cgiallows execution of CGI programs on your server. CGI programs are executable files residing in the /var/www/cgi-bindirectory and are used to dynamically generate data (usually HTML) for the remote browser when requested.

The mod_dir module is used to determine which files are returned automatically when a user tries to access a directory. The default is index.html. If you have users who create web pages on Windows systems, you should also include index.htm, like this:

DirectoryIndex index.html index.htm

mod_envcontrols how environment variables are passed to CGI and SSI scripts.

mod_expires is used to add an expiration date to content on your site by adding an Expiresheader to the HTTP response. Web browsers or cache servers don't cache expired content.

mod_headersis used to manipulate the HTTP headers of your server's responses. You can replace, add, merge, or delete headers as you see fit. The module supplies a Headerdirective for this. Ordering of the Headerdirective is important. A setfollowed by an unsetfor the same HTTP header removes the header altogether. You can place Headerdirectives almost anywhere within your configuration files. These directives are processed in the following order:

1. Core server

2. Virtual host

3. and .htaccessfiles

4. < Location >

5. < Files >

mod_infoprovides comprehensive information about your server's configuration. For example, it displays all the installed modules, as well as all the directives used in its configuration files.

mod_log_configdefines how your log files should look. See the "Logging" section for further information about this subject.

The mod_mimemodule tries to determine the MIME type of files from their extensions.

The mod_mime_magicmodule tries to determine the MIME type of files by examining portions of their content.

Using the mod_negotiationmodule, you can select one of several document versions that best suits the client's capabilities. You can select from among several options for which criteria to use in the negotiation process. You can, for example, choose among different languages, graphics file formats, and compression methods.

mod_proxyimplements proxy and caching capabilities for an Apache server. It can proxy and cache FTP, CONNECT, HTTP/0.9, and HTTP/1.0 requests. This isn't an ideal solution for sites that have a large number of users and therefore have high proxy and cache requirements. However, it's more than adequate for a small number of users.

mod_rewriteis the Swiss army knife of URL manipulation. It enables you to use powerful regular expressions to perform any imaginable manipulation of URLs. It provides rewrites, redirection, proxying, and so on. There's very little that you can't accomplish with this module.

See http://localhost/manual/misc/rewriteguide.html for a cookbook that gives you an in-depth explanation of what the mod_rewritemodule is capable of.

mod_setenvifallows manipulation of environment variables. Using small snippets of text-matching code known as regular expressions, you can conditionally change the content of environment variables. The order in which SetEnvIfdirectives appear in the configuration files is important. Each SetEnvIfdirective can reset an earlier SetEnvIfdirective when used on the same environment variable. Be sure to keep that in mind when using the directives from this module.

mod_spelingis used to enable correction of minor typos in URLs. If no file matches the requested URL, this module builds a list of the files in the requested directory and extracts those files that are the closest matches. It tries to correct only one spelling mistake.

You can use mod_statusto create a web page containing a plethora of information about a running Apache server. The page contains information about the internal status as well as statistics about the running Apache processes. This can be a great aid when you're trying to configure your server for maximum performance. It's also a good place to see whether something's amiss with your Apache server.

mod_sslprovides Secure Sockets Layer (version 2 and 3) and transport layer security (version 1) support for Apache. At least 30 directives exist that deal with options for encryption and client authorization and that can be used with this module.

mod_unique_idgenerates a unique request identifier for every incoming request. This ID is put into the UNIQUE_ID environment variable.

The mod_userdirmodule enables mapping of a subdirectory in each user's home directory into your web tree. The module provides several ways to accomplish this.

mod_vhost_aliassupports dynamically configured mass virtual hosting, which is useful for Internet service providers (ISPs) with many virtual hosts. However, for the average user, Apache's ordinary virtual hosting support should be more than sufficient.

There are two ways to serve virtual hosts on an Apache server. You can have one IP address with multiple CNAMEs, or you can have multiple IP addresses with one name per address. Apache has different sets of directives to handle each of these options. (You learn more about virtual hosting in Apache in the next section of this chapter.)

Again, the available options and features for Apache modules are too numerous to describe completely in this chapter. You can find complete information about the Apache modules in the online documentation for the server included with Fedora or at the Apache Software Foundation's website.