With Paseenger & nginx.

1. Install passenger and nginx from APT source
2. Install ruby using rvm
3. Config nginx passenger path, ruby to rvm source, and root to project public folder

I try ruby gem method to install both passenger and nginx at first(gem install passenger then rvmsudo passenger-install-nginx-module), but only nginx works. Maybe the mix different tutorial leads to this problem. After I removed passenger & nginx and installed again from APT, it finally worked.