Recipe 4.6 Mass Virtual Hosting with mod_vhost_alias

Problem

You want to host many virtual hosts, all of which have exactly the same configuration.

Solution

Use VirtualDocumentRoot and VirtualScriptAlias provided by mod_vhost_alias.

VirtualDocumentRoot /www/vhosts/%-1/%-2.1/%-2/htdocs VirtualScriptAlias  /www/vhosts/%-1/%-2.1/%-2/cgi-bin

Discussion

This recipe uses directives from mod_vhost_alias, which you may not have installed when you built Apache, as it is not one of the modules that is enabled by default.

These directives map requests to a directory built up from pieces of the hostname that was requested. Each of the variables represents one part of the hostname, so that each hostname is be mapped to a different directory.

In this particular example, requests for content from www.example.com is served from the directory /www/vhosts/com/e/example/htdocs, or from /www/vhosts/com/e/example/cgi-bin (for CGI requests). The full range of available variables is shown in Table 4-1.

Table 4-1. mod_vhost_alias variables

Variable	Meaning
%%	insert a %
%p	insert the port number of the virtual host
%M.N	insert (part of) the name

M and N may have positive or negative integer values, which have the following meanings (see Table 4-2).

Table 4-2. Meanings of variable values

Value	Meaning
0	The whole name
1	The first part of the name
-1	The last part of the name
2	The second part of the name
-2	The next-to-last part of the name
2+	The second, and all following, parts
-2+	The next-to-last, and all proceeding, parts

When the value is placed in the first part of the argument in the M part of %M.N it refers to parts of the hostname itself. When used in the second part the N refers to a particular letter from that part of the hostname. For example, in hostname www.example.com, the meanings of the variables are as shown in Table 4-3.

Table 4-3. Example values for the hostname www.example.com

Value	Meaning
%0	www.example.com
%1	www
%2	example
%3	com
%-1	com
%-2	example
%-3	www
%-2.1	e
%-2.2	x
%-2.3+	ample

Depending on the number of virtual hosts, you may wish to create a directory structure subdivided alphabetically by domain name, by top-level domain, or simply by hostname.

See Also

• http://httpd.apache.org/docs/mod/mod_vhost_alias.html

• http://httpd.apache.org/docs/vhosts/