Here is the minimum amount of configuration needed to force all web traffic (port 80, http) over to https (port 443 via SSL).

1) Create a .htaccess file that looks similar to this one:

RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*) https://www.example.com/$1 [L]

and place it at the root of the web server directory where you want to redirect the traffic. Restart apache.

2) If that doesn’t work, you might need to modify your apache config file’s AllowOverride setting. If you were trying to use a .htaccess file just inside of the /var/www directory, you might need to edit /etc/apache2/sites-enabled/[name-of-your-site]

...
   <Directory /var/www/>
        ...
        Options FollowSymLinks
        AllowOverride FileInfo
        ...
   </Directory>

NOTE: Your web site might have other directives for Options and AllowOverride, but the 2 that I have show are the bare minimum to get the .htaccess file working.