Note In most cases, a module requires its own configuration information. To simplify your life, you can put the configuration in a separate file and have httpd.conf pull it in with Include statements. This way, when you alter a module, you know where everything is.

Here are some of the popular Apache modules. Each is available on FreeBSD as a port of the same name, under /usr/ports/www. For example mod_gzip can be found in /usr/ports/www/mod/gzip.

mod_dav	Provides DAV (Distributed Authoring and Versioning) services.
mod_dtcl	Integrates a Tcl (Tool Command Language) interpreter with Apache, allowing rapid
	processing of Tcl CGI scripts.
mod_gzip	Compresses data before it's sent, if the browser supports it. This is well worth
	installing.
mod_mp3	Turns Apache into an MP3 streaming server.
mod_perl	Embeds Perl into your Apache server, allowing rapid handling of Perl CGI scripts.
mod_php3	Provides support for the PHP scripting language, version 3.
mod_php4	Provides support for the PHP scripting language, version 4.
mod_python Embeds Python into your Apache server, for rapid handling of Python CGIs.
mod_ruby	Embeds Ruby into Apache, permitting rapid handling of Ruby CGIs.

There are many other modules, but these are my favorites.

FrontPage and SSL

Microsoft's FrontPage poses a particular problem because, unfortunately, Microsoft's support for FrontPage Extensions on platforms other than its own is spotty at best. If you're interested in supporting FrontPage, install Microsoft's FrontPage Extensions module, apache13−fp port. It's very difficult to add this module later. Similarly, the Secure Sockets Layer (or SSL) module has a large footprint in Apache. (Not nearly as bad as FrontPage, mind you!) If you want SSL, aka https or secure Web pages), install the apache13−modssl port.

You might note that this leaves out the possibility of combining SSL and FrontPage, and you'd be right. Combining these at once is not for the faint of heart or for the inexperienced. Don't combine them until you're comfortable with both systems separately.

When the time comes for you to combine FrontPage with SSL, grab the latest version of the FrontPage Extensions from http://ftp://ftp.microsoft.com/products/frontpage. Extract the tarball and follow the instructions. If you run into problems, check the FreeBSD−isp mailing list archives. They're the people who are most likely to have experience with the latest versions.

[1]Every time I've implemented the quick−and−dirty method, I've had to go back months or years later and convert it to the more correct method. Start off right; you won't regret it.

[2]They won't tell you how to do it, either; they'll just berate you for considering it.

Virtual Hosting

Virtual hosting is having one server handle multiple Web sites. The server is configured to handle Web requests for each of these domains, and it returns the appropriate page for the domain. Many companies need a very small Web site, containing just a few pages of information and perhaps a CGI script or two to process requests for information. This is an excellent application for virtual hosts. I've had FreeBSD boxes handle thousands of these small domains without breaking a sweat

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or putting the system load up over 0.2. When each of those sites pays $9.95 a month to handle a couple dozen hits a day, you're quickly looking at real money on inexpensive hardware.

One common stumbling block to understanding virtual hosts is the belief that the "www" in a URL is some sort of magic incantation that points to a Web site. This is a common, but incorrect, idea. When you type a URL, such as http://www.absolutebsd.com/, you're telling your Web browser to go look for a machine named http://www.absolutebsd.com/, connect to port 80, and see what it has to offer. You could type in http://mail.absolutebsd.com/, and the client would look for a machine with that name.

The trick underlying a virtual host is very simple: Many hostnames point to one machine. The problem on the server side is to differentiate between the requests for multiple domains, and then to serve up the appropriate pages. This leads to two different styles of virtual hosts: name−based and IP−based.

Name−Based Virtual Hosts

Modern Web browsers, such as Netscape 3 and Internet Explorer 4 and later, include the name of the Web site that they're trying to reach when they request a Web page from a server. This makes it possible for the server to differentiate between requests for the various Web sites it serves. If you are fairly sure that your clients are not using Netscape 2 or Internet Explorer 3, you can tell your server to use these names to identify virtual hosts. Name−based virtual hosts are the standard almost everywhere, and should be your standard unless you have a good reason otherwise.

Place your virtual host configuration at the end of the httpd.conf file, or even in a separate file (using the httpd.conf keyword Include to pull that file in). Do not mix your virtual host configurations with your main server configuration, or you will get quite confused when you have to sort it out.

To configure name−based virtual hosts, first tell Apache which IP address to use for them with the NameVirtualHost httpd.conf directive. While multiple name−based virtual hosts can live on one IP address, Apache must know which IP address to bind these to:

...............................................................................................

NameVirtualHost 192.168.33.254

...............................................................................................

Once this is set, any requests that come in to that IP address will be treated as a named virtual−host request. Now you have to tell Apache where to get information on each virtual host. At the very least, each virtual host needs the name of the Web site and the directory where the HTML documents for that Web site can be found. Here's an example of a basic virtual host that only needs these two items:

...............................................................................................

<VirtualHost 192.168.33.254> ServerName www.AbsoluteBSD.com DocumentRoot /home/mwlucas/www

</VirtualHost>

...............................................................................................

The <VirtualHost> and </VirtualHost> labels tell Apache that the information between them is for a single virtual host, and they include the IP address of the virtual host.

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The ServerName directive tells Apache the name of this virtual host. The server uses this entry to handle requests for http://www.absolutebsd.com/.

Finally, the DocumentRoot entry tells Apache where to find the HTML documents that make up this site.

It works this way: When a browser sends a Web request to the virtual host IP address of 192.168.33.254 and asks for http://www.absolutebsd.com/, Apache pulls the documents out of the directory /home/mwlucas/www and returns them to the client.

IP−Based Virtual Hosts

Not all browsers send the site name along with the Web request. In fact, this was the standard in the earlier days of the Internet (Netscape 2 and Internet Explorer 3), when IP addresses were so plentiful it seemed they could never run out. Browser clients assumed that they could just make a connection to the Web server on port 80, and the only thing that would be on that port was that particular site.

You might think that that time vanished with the Apple II and Betamax, but no. In 2001 I came across a corporate network that had 12,000 desktops running a Mosaic−based Web browser on Windows for Workgroups. This browser is so old that it expected every Web site to have a unique IP address and did not transmit the site name with the Web request. And the company's intranet Web server had to support these clients. While You'll probably never have to worry about these sorts of clients on the public Internet, you should still know how to configure them in case you encounter this sort of situation.

Additionally, sites that use SSL expect to have a single hostname for a single IP. To combine SSL with virtual hosts, you must use IP−based virtual hosts.

To use IP−based virtual hosts, specify the IP address in the VirtualHost space, much like you do for name−based virtual hosts. This looks exactly like the VirtualHost setup used by name−based virtual hosts, except that the IP address in the VirtualHost space is unique. The only difference between setting up an IP−based virtual host and a name−based virtual host is that IP−based virtual hosts don't need the NameVirtualHost directive.

Here's a minimal setup of an IP−based virtual host:

...............................................................................................

<VirtualHost 209.69.178.18> ServerName www.blackhelicopters.org DocumentRoot /home/mwlucas/www2 </VirtualHost>

...............................................................................................

Any request that arrives at port 80 on the IP address 209.69.178.18 will receive the HTML in /home/mwlucas/www2.

Tweaking Virtual Hosts

Once you have the minimal virtual hosts (described in the previous sections) working, you can add additional touches to them. Here we'll discuss various virtual−host options that will work with both

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IP−based and name−based virtual hosts, and how they can be used.

Port Numbers

Different documents can be served on different ports. (you've probably seen this before, when a hostname in a URL has a colon followed by a number.) If Apache is listening on ports 80 and 81, for example, you could have a different virtual host on each port, as long as you add the port number after the IP address in the VirtualHost directive.

For example, here's a configuration that creates two different sites (http://www.absolutebsd.com/ and http://data.absolutebsd.com:8080/) using two similar virtual hosts on different ports. Both sites are on the same IP address, but on different ports.

...............................................................................................

<VirtualHost 209.69.178.18:80> ServerName www.AbsoluteBSD.com DocumentRoot /home/mwlucas/www </VirtualHost>

<VirtualHost 209.69.178.18:8080> ServerName data.AbsoluteBSD.com DocumentRoot /home/mwlucas/data </VirtualHost>

...............................................................................................

Virtual Host Logs

By default, virtual hosts write their logs to the default Apache log, but you might want to split the logs out by virtual host. (This is common when you're running a commercial Web server and want each customer to get their own logs.) Do so with the ErrorLog and TransferLog directives, both of which take the name of the log file as an argument:

...............................................................................................

<VirtualHost 209.69.178.18:80> ServerName www.AbsoluteBSD.com DocumentRoot /home/mwlucas/www

ErrorLog /home/mwlucas/absolutebsd.com−error−log TransferLog /home/mwlucas/absolutebsd.com−access−log </VirtualHost>

...............................................................................................

The TransferLog directive can also take the type of information to be logged as a second argument. We saw the standard log styles in the discussion of the LogFormat directive (in the "Log Format" section) earlier in this chapter.

Options and AllowOverride

By default, virtual hosts inherit the Options and AllowOverride settings of the root directory. As a reminder, here's a sample configuration for the root directory:

...............................................................................................

<Directory />

Options AuthConfig Limit

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