Apache HTTP Server Version 2.5

Apache > HTTP Server > Documentation > Version 2.5 > 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 usually 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.

### See also

- 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 `SITE.example.com` for each user, and serve their content out of `/home/SITE/www`. However, we want `www.example.com` to be omitted from this mapping.

Solution:

      RewriteEngine on

      RewriteMap    lowercase int:tolower

      RewriteCond   %{HTTP_HOST} !^www\.
      RewriteCond   ${lowercase:%{HTTP_HOST}}   ^([^.]+)\.example\.com$
      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.

  The first `RewriteCond` checks to see if the hostname starts with `www.`, and if it does, the rewriting is skipped.

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