Here is my Gem Environment:
RubyGems Environment:
  - RUBYGEMS VERSION: 1.3.5
  - RUBY VERSION: 1.8.7 (2010-01-10 patchlevel 249) [x86_64-linux]
  - INSTALLATION DIRECTORY: /var/lib/gems/1.8
  - RUBY EXECUTABLE: /usr/bin/ruby1.8
  - EXECUTABLE DIRECTORY: /var/lib/gems/1.8/bin
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-linux
  - GEM PATHS:
     - /var/lib/gems/1.8
     - /home/haonanzhang/.gem/ruby/1.8
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :benchmark => false
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - http://gems.rubyforge.org/
I want to install taps to export a database from Heroku.
But when I run sudo gem install taps, I get the following error.
ERROR:  Error installing taps:
        ERROR: Failed to build gem native extension.
/usr/bin/ruby1.8 extconf.rb
extconf.rb:3:in `require': no such file to load -- mkmf (LoadError)
        from extconf.rb:3
Any suggestions?
Thanks.