This article applies to Ubuntu with Apache 2, MySQL 5 and PHP 5 installed from the package manager.

When you start using Drupal on Ubuntu, one of the first things to do is to enable clean urls. That page will first ask you to run the clean URL test, which will show you if the underlying Apache infrastructure is ready for this or not. It it's ready, clicking the test link should bring you back to the same page, but with the radiobuttons enabled. Otherwise, you will get a "page not found" error.

On Ubuntu, the "page not found" error is indeed what you will get first! Here's how to fix this in 3 easy steps:

1. Ensure that mod_rewrite is enabled for Apache 2:
    % sudo a2enmod rewrite
2. Edit Apache 2 configuration to allow Drupal's .htaccess file to be used. In file /etc/apache2/sites-enabled/000-default, inside the tag Directory /var/www/, replace the line
   AllowOverride none
   with
   AllowOverride All
3. Restart Apache 2:
   % sudo /etc/init.d/apache2 restart