Debian Passenger error: cannot load such file -- bundler (LoadError) - ruby-on-rails

Question

I am running Apache on my Raspberry Pi (Raspbian) and struggling to get Passenger working properly with my site. When I go to visit my site (which is set up as a VirtualHost), I get the error: "cannot load such file -- bundler". The first line of the backtrace is
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb
To install Passenger, I followed the instructions here: http://www.modrails.com/documentation/Users%20guide%20Apache.html#install_on_debian_ubuntu.
In particular, I ran the command
sudo apt-get install libapache2-mod-passenger
This link says, "The Apache package provides configuration snippets for you, so you don’t need to modify any Apache configuration to get it to load Phusion Passenger". The way the installation went on my machine was that it automatically added and enabled the passenger module through the files "passenger.conf" and "passenger.load":
passenger.conf:
<IfModule mod_passenger.c>
PassengerRoot /usr
PassengerRuby /usr/bin/ruby
</IfModule>
passenger.load:
LoadModule passenger_module /usr/lib/apache2/modules/mod_passenger.so
Running "gem env" gives me the following output:
RubyGems Environment:
- RUBYGEMS VERSION: 2.0.7
- RUBY VERSION: 2.0.0 (2013-06-27 patchlevel 247) [armv6l-linux-eabihf]
- INSTALLATION DIRECTORY: /home/user/.rvm/gems/ruby-2.0.0-p247
- RUBY EXECUTABLE: /home/user/.rvm/rubies/ruby-2.0.0-p247/bin/ruby
- EXECUTABLE DIRECTORY: /home/user/.rvm/gems/ruby-2.0.0-p247/bin
- RUBYGEMS PLATFORMS:
- ruby
- armv6l-linux
- GEM PATHS:
- /home/user/.rvm/gems/ruby-2.0.0-p247
- /home/user/.rvm/gems/ruby-2.0.0-p247#global
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :backtrace => false
- :bulk_threshold => 1000
- REMOTE SOURCES:
- https://rubygems.org/
I tried looking all over for a mod_passenger.so file elsewhere in the file system with no luck. I am reluctant to simply reinstall rails or passenger because I am unsure what the implications will be for the modules and configuration. Any advice is appreciated, thanks!

Answer 1

Maybe you didn't configure your app to use Ruby 2.0.0? If you don't do that explicitly, it will use the default Ruby, which is /usr/bin/ruby. This section from the manual tells you how to specify a different Ruby: http://www.modrails.com/documentation/Users%20guide%20Apache.html#PassengerRuby
Note that multiple Ruby supports requires Phusion Passenger >= 4.0.0.

Answer 2

The problem ended up being that I needed to set the environment variable for the GEM_PATH within a .htaccess file!