Canonical Redirect

For Apache2 Ubuntu 12.04 LTS the VirtualHost for sites is in /etc/apache2/sites-available

sudo vi www.example.com

add this line

Redirect 301 http://example.com http://www.example.com/

<VirtualHost *:80>
     ServerAdmin webmaster@localhost
     ServerName example.com
     ServerAlias www.example.com
     Redirect 301 http://example.com http://www.example.com/
     DocumentRoot /var/www/www.example.com/
</VirtualHost>