When using passenger with an app deployed to a sub-uri most details of app paths are handled automatically. However, when deploying an app the precompiled assets using helpers such as asset_path will get the wrong path because it doesn’t know about the sub-uri. The solution is to set Rails.application.config.action_controller.relative_url_root in an initializer or environment to the sub-uri path. I learned this from the font-awesome rails documentation but this is a common issue as I found a lot of people running into similar problems wherever assets where being precompiled.

• font-awesome-rails issue 74
• font-awesome-rails issue 402
• jquery-ui-rails issue 54
• rails issue 3365
• rails issue 8941

Be clear this is:

Rails.application.config.action_controller.relative_url_root

and not:

Rails.application.config.relative_url_root

Also this can be accomplished by setting the environmental variable RAILS_RELATIVE_URL_ROOT but I think that will usually be more work but maybe there are instances where that is the better solution.

It would be wise to include this in the passenger documentation for deploying to a sub-uri as this is where most people could be made aware of the importance of this detail and how not addressing it could lead to problems later.