when i first installed mod_ruby on my small debian and later on ( after determining it was not fast enough ) i needed to chagne to passenger for my apache

Now i have got the issue, the passenger is effectively loaded through the apache, however is not used, despite the fact that i set up everything properly, like:

<VirtualHost *>
        ServerAdmin webmaster@localhost
        ServerName xyz
        DocumentRoot /var/www/vhosts/default/htdocs/
        RailsBaseURI /rails

Instad from the the passenger the cgi - module can be used for exhibiting rails-applications... ( basically unload the cgi.conf and cgi-load in the "sites-enabled" folder, it isn't working any longer... however still it works basically unload the passenger.load and passenger.conf files... )

So, how do i pressure the apache to make use of the passenger to show rails sites?

Presuming you've passenger installed and set up properly with Apache ... Your DocumentRoot must point in the public directory of the rails application. Here is a working VirtualHost directive:

<VirtualHost *:80>
  ServerName myapp.local
  DocumentRoot "/path/to/myapp/public"
  RailsEnv development
  <directory "/path/to/myapp/public">
    Order allow,deny
    Allow from all

In advance, also make certain that named virtual hosts are switched on:

NameVirtualHost *:80

And that you really possess the passenger model set up properly. For instance:

LoadModule passenger_module /path/to/ruby/gems/1.8/gems/passenger-2.2.5/ext/apache2/mod_passenger.so
PassengerRoot /path/to/ruby/gems/1.8/gems/passenger-2.2.5
PassengerRuby /path/to/bin/ruby

Have you reconfigure the relative_url_root inside your rails application? For instance, in config/environment.rb:

config.action_controller.relative_url_root = "/rails"