How can I redirect any ServerAlias to the respective ServerName?

Question

I want to 301 redirect all example.org to www.example.org. The following example is doing just that, but it's got a lot of noise to it and is thus hard to maintain and error prone:

<VirtualHost 192.0.2.123:80>
        ServerName      example.org
        RedirectPermanent       /               http://www.example.org
</VirtualHost>
<VirtualHost 192.0.2.123:80>
        ServerName      www.example.org
        DocumentRoot    /usr/local/www/example
</VirtualHost>

Do you happen to know if there's some shorter version for the whole thing above?

Something like this pseudo-config:

<VirtualHost 192.0.2.123:80>
        ServerName      www.example.org
        ServerAlias     example.org
#       Redirect-Every-ServerAlias-To-ServerName
        DocumentRoot    /usr/local/www/example
</VirtualHost>

So that way I would just need to provide every subdomain that should be redirected under ServerAlias ?

Solution

Use mod_rewrite, something like this:

RewriteEngine On
RewriteCond %{HTTP_HOST}  !^www.example.org [nocase]
RewriteRule ^(.*)$        http://www.example.org$1 [last,redirect=301]

Comments

[LazyOne]

You can use mod_rewrite to redirect all requests to example.org to a www.example.org -- only 2 lines (well, 3 including engine activation directive).

[Ladadadada]

A small improvement to this is to use !^www.example.org in your RewriteCond which will make it continue working no matter how many ServerAlias directives your vhost has.

[Ladadadada]

Your answer is essentially the same as the example he gave of what he is currently doing.

[OrangeDog]

You can also use %{SERVER_NAME} in the expressions