I was getting 403 errors after deploying my newest Sinatra app with Passenger.

Turns out Passenger assumes and requires a /public folder.

This app is so tiny and new, it didn’t have one yet – so I was pointing Passenger at the app’s root. Resulting in the 403 errors.

Solution: Create an empty /public folder and restart Apache. Ta Da. Like magic.

If you’re still having issues – confirm your LoadModule passenger_module path is correct, mine looks like this:
opt/local/lib/ruby/gems/1.8/gems/passenger-2.2.7/ext/apache2/mod_passenger.so

After updating the Passenger gem to 2.2.7, my LoadModule path was way off, not helping the deployment troubleshooting efforts.