The new download file checksums match yours now. I followed your backport instructions for redis-server v2.8.6

I still get an error.

$ tail /var/log/apache2/error.log

     in 'virtual Passenger::ApplicationPool2::ProcessPtr Passenger::ApplicationPool2::SmartSpawner::spawn(const Passenger::ApplicationPool2::Options&)' (SmartSpawner.h:744)
     in 'void Passenger::ApplicationPool2::Group::spawnThreadRealMain(const SpawnerPtr&, const Passenger::ApplicationPool2::Options&, unsigned int)' (Implementation.cpp:782)

[ 2014-05-12 15:58:39.3563 2096/7f9038264700 agents/HelperAgent/RequestHandler.h:1975 ]: [Client 20] Cannot checkout session. An error occurred while starting up the preloader: it did not write a startup response in time.
Error page:

/var/www/canvas/vendor/bundle/ruby/1.9.1/bundler/gems/rails-e86daf8ff727/activesupport/lib/active_support/inflector.rb:3:in `<top (required)>': iconv will be deprecated in the future, use String#encode instead.
NOTE: Gem.source_index is deprecated, use Specification. It will be removed on or after 2011-11-01.
Gem.source_index called from /var/www/canvas/vendor/bundle/ruby/1.9.1/bundler/gems/rails-e86daf8ff727/railties/lib/rails/gem_dependency.rb:21.

The browser says:

Web Application could not be started.

Phusion Passenger has listed more information about the error below.

/var/www/canvas/vendor/bundle/ruby/1.9.1/bundler/gems/rails-e86daf8ff727/activesupport/lib/active_support/inflector.rb:3:in `<top (required)>': iconv will be deprecated in the future, use String#encode instead.
NOTE: Gem.source_index is deprecated, use Specification. It will be removed on or after 2011-11-01.
Gem.source_index called from /var/www/canvas/vendor/bundle/ruby/1.9.1/bundler/gems/rails-e86daf8ff727/railties/lib/rails/gem_dependency.rb:21.