Phusion Passenger Error: You have activated rack 1.2.1, but your Gemfile requires rack 1.2.2

try to restart your server after edit in your Gemfile and put this: gem 'rack', '1.2.1'

This works in Rails 3.0.x & Passenger 3.0.15

create a file:

config/setup_load_paths.rb

with content:

require 'rubygems'require 'bundler/setup'

Passenger will then load the rack gem specified in your Gemfile.lock

After long periods of inactivity, I've been receiving a similar error for a couple of Sinatra applications on a DreamHost VPS:

Phusion Passenger Error: You have activated rack 1.2.1, but your Gemfile requires rack 1.3.0.

Like how @aren55555 described, if you simply refresh the page, the error goes away. Here is something that I discovered about the server configuration:

[psXXXXX]$ gem envRubyGems Environment:  - RUBYGEMS VERSION: 1.3.6  - RUBY VERSION: 1.8.7 (2008-08-11 patchlevel 72) [x86_64-linux]  - INSTALLATION DIRECTORY: /home/XXXXXXXXX/.gems/  - RUBY EXECUTABLE: /usr/bin/ruby1.8  - EXECUTABLE DIRECTORY: /home/XXXXXXXXX/.gems/bin  - RUBYGEMS PLATFORMS:    - ruby    - x86_64-linux  - GEM PATHS:     - /home/XXXXXXXXX/.gems/               <-- Rack 1.3.0 Gem was installed here     - /usr/lib/ruby/gems/1.8               <-- Rack 1.2.1 Gem was installed here  - GEM CONFIGURATION:     - :update_sources => true     - :verbose => true     - :benchmark => false     - :backtrace => false     - :bulk_threshold => 1000  - REMOTE SOURCES:     - http://rubygems.org/

My guess as to what was happening is, after Passenger "wakes up", for some reason it's looking first (or perhaps only) to the Gems at the system-level, selecting Rack 1.2.1 as the latest version. My short-term hacky solution was simply to install Rack 1.3.0 there:

gem install rack -v 1.3.0 --install-dir /usr/lib/ruby/gems/1.8

It seems to have worked. Hope this is helpful to anyone else tearing their hair out there.