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