How to redirect non-www to www

Howto 301 ( permanent ) redirect non www to www

301 (permanent) redirect all non-www requests to www.

Apache webserver with mod_rewrite enabled; apache.conf or .htaccess file.

RewriteEngine On

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

This will redirect requests to all pages to www. domain.