Enable Ubuntu public_html user directory for Apache

The steps to make http://localhost/~username works in Ubuntu.

1. Create public_html directory in home directory
   mkdir ~/public_html
2. Enable the user directory
   cd /etc/apache2/mods-enabled
   sudo ln -s ../mods-available/userdir.conf userdir.conf
   sudo ln -s ../mods-available/userdir.load userdir.load
3. Restart Apache
   sudo /etc/init.d/apache2 restart