Unable to start the Phusion Passenger watchdog?

Question

I have done a Phusion Passenger setup on Ubuntu 10.04, with Apache2. Whenever I restart the Apache server I got the following error message, and the Rails application is not

Answer 1

I ran into the same problem when compiling from source, but it was intermittent, which was really frustrating (I think it has to w/ Rails environments). We couldn't use the passenger-install-apache2-module/passenger-install-nginx-module scripts, because we needed a customized nginx installation.

I finally fixed the problem by going to whatever the passenger-config --root is, then running: rake nginx.

Update February 2016 (by Passenger author):

The officially supported method to compile PassengerAgent (without also compiling Nginx, as passenger-install-nginx-module does) is with this command:

passenger-config compile-agent

Passenger 5.0.26 and later will automatically detect the error described in this StackOverflow question, and will automatically suggest running the above command.