redirecting www.subdomain.example.com to subdomain.example.com

I've had some users trying to access a site that is registered as subdomain.example.com with www.subdomain.example.com.

is there some sort of .htaccess rule I can add to redirect people that arri开发者_如何学Gove using www.subdomain.example.com to subdomain.example.com?

Also, do I have to change DNS stuff?

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Sure, use a directive like:

<VirtualHost *:80> 
    ServerName www.subdomain.example.com 
    Redirect permanent / http://subdomain.example.com/ 
</VirtualHost> 

Apache automatically preserves anything after the / when using the Redirect directive, which is a common misconception about why this method won't work (when in fact it does).

Also, yes you will need to change DNS records, because www.subdomain.example.com is a distinct hostname that needs its own A (or CNAME) record to point the browser to an appropriate server in the first place.

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RewriteCond %{HTTP_HOST} ^www.subdomain.domain.com
RewriteRule (.*) http://subdomain.domain.com/$1 [R=301,L]

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You need to add a virtual host directive in httpd.conf and Redirect Permament to the correct subdomain and add the additional DNS entry (CNAME is fine)