Rewrite

# Dynamic mass virtual hosts with mod_rewrite

This document supplements the mod_rewrite reference documentation. It describes how you can use mod_rewrite to create dynamically configured virtual hosts.

mod_rewrite is not the best way to configure virtual hosts. You should first consider the alternatives before resorting to mod_rewrite. See also the "how to avoid mod_rewrite document.

Module documentation
mod_rewrite introduction
Redirection and remapping
Controlling access
Proxying
RewriteMap
Advanced techniques
When not to use mod_rewrite

# Virtual Hosts For Arbitrary Hostnames

Description:

  We want to automatically create a virtual host for every hostname which resolves in our domain, without having to create new VirtualHost sections.

  In this recipe, we assume that we'll be using the hostname `www.SITE.example.com` for each user, and serve their content out of `/home/SITE/www`.

Solution:
  RewriteEngine on
  RewriteMap lowercase int:tolower
  RewriteCond %{lowercase:%{HTTP_HOST}} ^www\.([^.]+)\.example\.com$
  RewriteRule ^(.*) /home/%1/www$1
Discussion

  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.

  The internal `tolower` 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.

  Parentheses used in a RewriteCond are captured into the backreferences `%1`, `%2`, etc, while parentheses used in RewriteRule are captured into the backreferences `$1`, `$2`, etc.

  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 mod_vhost_alias instead, as it will much more gracefully handle anything beyond serving static files, such as any dynamic content, and Alias resolution.

# Dynamic Virtual Hosts Using mod_rewrite

This extract from `httpd.conf` does the same thing as the first example. The first half is very similar to the corresponding part above, except for some changes, required for backward compatibility and to make the `mod_rewrite` part work properly; the second half configures `mod_rewrite` to do the actual work.

Because `mod_rewrite` runs before other URI translation modules (e.g., `mod_alias`), `mod_rewrite` must be told to explicitly ignore any URLs that would have been handled by those modules. And, because these rules would otherwise bypass any `ScriptAlias` directives, we must have `mod_rewrite` explicitly enact those mappings.

# 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
<Directory /www/hosts>
# ExecCGI is needed here because we can't force
# CGI execution in the way that ScriptAlias does
Options FollowSymLinks ExecCGI
</Directory>
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]

# Using a Separate Virtual Host Configuration File

This arrangement uses more advanced mod_rewrite 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.

The `vhost.map` file should look something like this:

customer-1.example.com /www/customers/1
customer-2.example.com /www/customers/2
# ...
customer-N.example.com /www/customers/N

The `httpd.conf` should contain the following:

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]