1. You want to deploy a Sinatra application with Passenger on Dreamhost
2. You’re using a Dreamhost shared hosting account
3. You’re application relies on gems that aren’t installed globally on Dreamhost
4. You’ve got the gems you need installed locally like this

Then you’ll want to include something like this in your rackup file:

This will make sure your locally installed gems will be available to your application. Maybe my google skills are getting rusty, but it took me a while to find this solution. Here’s the original source.