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<parentdocument href="./">Rewrite</parentdocument>

<title>Dynamic mass virtual hosts with mod_rewrite</title>

<summary>

<p>This document supplements the <module>mod_rewrite</module>

<a href="/mod/mod_rewrite.html">reference documentation</a>. It describes

how you can use <module>mod_rewrite</module> to create dynamically

configured virtual hosts.</p>

<note type="warning">mod_rewrite is not the best way to configure

virtual hosts. You should first consider the <a

href="/vhosts/mass.html">alternatives</a> before resorting to

mod_rewrite. See also the "<a href="avoid.html#vhosts">how to avoid

mod_rewrite</a> document.</note>

</summary>

<seealso><a href="/mod/mod_rewrite.html">Module documentation</a></seealso>

<seealso><a href="intro.html">mod_rewrite introduction</a></seealso>

<seealso><a href="remapping.html">Redirection and remapping</a></seealso>

<seealso><a href="access.html">Controlling access</a></seealso>

<seealso><a href="proxy.html">Proxying</a></seealso>

<seealso><a href="rewritemap.html">RewriteMap</a></seealso>

<seealso><a href="advanced.html">Advanced techniques</a></seealso>

<seealso><a href="avoid.html">When not to use mod_rewrite</a></seealso>

<section id="per-hostname">

<title>Virtual Hosts For Arbitrary Hostnames</title>

<dl>

<dt>Description:</dt>

<dd>

<p>We want to automatically create a virtual host for every hostname

which resolves in our domain, without having to create

new VirtualHost sections.</p>

<p>In this recipe, we assume that we'll be using the hostname

<code>www.<strong>SITE</strong>.example.com</code> for each

user, and serve their content out of

<code>/home/<strong>SITE</strong>/www</code>.</p>

</dd>

<dt>Solution:</dt>

<dd>

<highlight language="config">

RewriteEngine on

RewriteMap lowercase "int:tolower"

RewriteCond "${lowercase:%{<strong>HTTP_HOST</strong>}}" "^www\.<strong>([^.]+)</strong>\.example\.com$"

RewriteRule "^(.*)" "/home/<strong>%1</strong>/www$1"

</highlight></dd>

<dt>Discussion</dt>

<dd>

<note type="warning">You will need to take care of the DNS

resolution - Apache does

not handle name resolution. You'll need either to create CNAME

records for each hostname, or a DNS wildcard record. Creating DNS

records is beyond the scope of this document.</note>

<p>The internal <code>tolower</code> RewriteMap directive is used to

ensure that the hostnames being used are all lowercase, so that there is

no ambiguity in the directory structure which must be created.</p>

<p>Parentheses used in a <directive

module="mod_rewrite">RewriteCond</directive> are captured into the

backreferences <code>%1</code>, <code>%2</code>, etc, while parentheses

used in <directive module="mod_rewrite">RewriteRule</directive> are

captured into the backreferences <code>$1</code>, <code>$2</code>,

etc.</p>

<p>

As with many techniques discussed in this document, mod_rewrite really

isn't the best way to accomplish this task. You should, instead,

consider using <module>mod_vhost_alias</module> instead, as it will much

more gracefully handle anything beyond serving static files, such as any

dynamic content, and Alias resolution.

</p>

</dd>

</dl>

</section>

<section id="simple.rewrite"><title>Dynamic

Virtual Hosts Using <module>mod_rewrite</module></title>

<p>This extract from <code>httpd.conf</code> does the same

thing as <a href="#per-hostname">the first example</a>. The first

half is very similar to the corresponding part above, except for

some changes, required for backward compatibility and to make the

<code>mod_rewrite</code> part work properly; the second half

configures <code>mod_rewrite</code> to do the actual work.</p>

<p>Because <code>mod_rewrite</code> runs before other URI translation

modules (e.g., <code>mod_alias</code>), <code>mod_rewrite</code> must

be told to explicitly ignore any URLs that would have been handled

by those modules. And, because these rules would otherwise bypass

any <code>ScriptAlias</code> directives, we must have

<code>mod_rewrite</code> explicitly enact those mappings.</p>

<highlight language="config">

# get the server name from the Host: header

UseCanonicalName Off

# splittable logs

LogFormat "%{Host}i %h %l %u %t \"%r\" %s %b" vcommon

CustomLog "logs/access_log" vcommon

&lt;Directory "/www/hosts"&gt;

# ExecCGI is needed here because we can't force

# CGI execution in the way that ScriptAlias does

Options FollowSymLinks ExecCGI

&lt;/Directory&gt;

RewriteEngine On

# a ServerName derived from a Host: header may be any case at all

RewriteMap lowercase "int:tolower"

## deal with normal documents first:

# allow Alias /icons/ to work - repeat for other aliases

RewriteCond "%{REQUEST_URI}" "!^/icons/"

# allow CGIs to work

RewriteCond "%{REQUEST_URI}" "!^/cgi-bin/"

# do the magic

RewriteRule "^/(.*)$" "/www/hosts/${lowercase:%{SERVER_NAME}}/docs/$1"

## and now deal with CGIs - we have to force a handler

RewriteCond "%{REQUEST_URI}" "^/cgi-bin/"

RewriteRule "^/(.*)$" "/www/hosts/${lowercase:%{SERVER_NAME}}/cgi-bin/$1" [H=cgi-script]

</highlight>

</section>

<section id="xtra-conf"><title>Using a Separate Virtual Host Configuration File</title>

<p>This arrangement uses more advanced <module>mod_rewrite</module>

features to work out the translation from virtual host to document

root, from a separate configuration file. This provides more

flexibility, but requires more complicated configuration.</p>

<p>The <code>vhost.map</code> file should look something like

this:</p>

<example>

customer-1.example.com /www/customers/1<br />

customer-2.example.com /www/customers/2<br />

# ...<br />

customer-N.example.com /www/customers/N<br />

</example>

<p>The <code>httpd.conf</code> should contain the following:</p>

<highlight language="config">

RewriteEngine on

RewriteMap lowercase "int:tolower"

# define the map file

RewriteMap vhost "txt:/www/conf/vhost.map"

# deal with aliases as above

RewriteCond "%{REQUEST_URI}" "!^/icons/"

RewriteCond "%{REQUEST_URI}" "!^/cgi-bin/"

RewriteCond "${lowercase:%{SERVER_NAME}}" "^(.+)$"

# this does the file-based remap

RewriteCond "${vhost:%1}" "^(/.*)$"

RewriteRule "^/(.*)$" "%1/docs/$1"

RewriteCond "%{REQUEST_URI}" "^/cgi-bin/"

RewriteCond "${lowercase:%{SERVER_NAME}}" "^(.+)$"

RewriteCond "${vhost:%1}" "^(/.*)$"

RewriteRule "^/(.*)$" "%1/cgi-bin/$1" [H=cgi-script]

</highlight>

</section>

</manualpage>