# Check source. gem sources # Rebuild index for affected sources, e.g. gem generate_index http://gems.rubyforge.org # -d: detail gem search ^rails [-d] gem install GEMNAME --source http://rubygems.org gem list # Read doc for installed GEMNAME: ri $GEMNAME # Read doc on http server: gem server # Fetch and read without installation. If you doubt about security of GEMNAME: gem fetch $GEMNAME gem unpack $GEMNAME gem build GEMNAME.gemspec gem install gemname-version.gem # Specify that a gem should come from a git repository with a .gemspec at its root # Because Rubygems lacks the ability to handle gems from git, any gems installed from a git repository will not show up in gem list. # They will, however, be available after running Bundler.setup. gem 'nokogiri', :git => 'https://github.com/tenderlove/nokogiri.git' # What if # /usr/bin/ruby extconf.rb # mkmf.rb can't find header files for ruby at /usr/lib/ruby/ruby.h sudo yum -y install ruby-devel # See environment. gem env # Notice the two sections for: # INSTALLATION DIRECTORY # GEM PATHS # gem sources should at least contain https://rubygems.org. If not gem sources -a https://rubygems.org
SO provides a brief introduction to: gems, RubyGems, bundler, rvm, gemsets.
Can't install passenger
Ref. Put passenger gem to Gemfile.