1. enable mod_rewrite: a2enmod rewrite
2. overwrite index.php via .htaaccess
RewriteEngine on
RewriteCond $1 !^(index\.php|public|\.txt)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?$1
3. $config['index_page'] = 'index.php' -> $config['index_page'] = '';