Hi, why not just start from a ruby-less system by merely installing redmine and redmine-sqlite? All dependencies will be fullfilled by apt-get or aptitude.
According to /usr/share/doc/redmine/README.Debian, the standalone redmine can than already be tested via webrick. Also, I think, the application's root directory is /usr/share/redmine/config. That's where I installed my unicorn configuration file. >From /usr/share/doc/redmine/README.Debian I understand that the apache2-passenger*.conf should be installed there. As I wrote already, running redmine from a sub-URI is another step. Regards, Jörg.