Rather a simple question I believe, is it possible to install passenger when nginx is already installed on your webserver?
If the answer is Yes, I already performed these actions:
At this very moment I already have nginx installed (for my PHP applications) and next I did a checkout of the passenger's git repository:
git clone https://github.com/FooBarWidget/passenger.git
* Starting Web Server nginx
nginx: [emerg] unknown directive "passenger_root" in /etc/nginx/nginx.conf:19
I think your problem is that the passenger module is not present in nginx.
All the passenger dependent directives you've described (passenger_root, passenger_ruby, passenger_enabled) are available only when the passenger module is attached to nginx. This is why you have to compile nginx with
Unfortunately, I don't know of any method to enable passenger module without re-installing nginx. But, according to http://wiki.nginx.org/Modules, "Nginx modules must be selected at compile-time.", so there could be a chance that there isn't a way to do that.