Не удалось создать собственное расширение gem-Rails install

я устанавливал Ruby on Rails на основе инструкции из онлайн-класса edX.

вот список команд терминала, и, где это уместно, соответствующий вывод:

$ sudo apt-get install ruby1.9.1

установки

$ wget http://production.cf.rubygems.org/rubygems/rubygems-1.8.24.tgz

$ tar zxvf ruby-1.8.24.tgz

$ cd ruby-1..8.24

$ sudo ruby setup.rb

RubyGems 1.8.24 installed



== 1.8.24 / 2012-04-27



* 1 bug fix:



  * Install the .pem files properly. Fixes #320

  * Remove OpenSSL dependency from the http code path





------------------------------------------------------------------------------



RubyGems installed the following executables:

    /usr/bin/gem1.9.1

до сих пор все выглядело нормально, но я попытался установить рельсы и потерпел неудачу:

$ sudo gem install rails

Fetching: i18n-0.6.1.gem (100%)

Fetching: multi_json-1.3.6.gem (100%)

Fetching: activesupport-3.2.8.gem (100%)

Fetching: builder-3.0.3.gem (100%)

Fetching: activemodel-3.2.8.gem (100%)

Fetching: rack-1.4.1.gem (100%)

Fetching: rack-cache-1.2.gem (100%)

Fetching: rack-test-0.6.1.gem (100%)

Fetching: journey-1.0.4.gem (100%)

Fetching: hike-1.2.1.gem (100%)

Fetching: tilt-1.3.3.gem (100%)

Fetching: sprockets-2.1.3.gem (100%)

Fetching: erubis-2.7.0.gem (100%)

Fetching: actionpack-3.2.8.gem (100%)

Fetching: arel-3.0.2.gem (100%)

Fetching: tzinfo-0.3.33.gem (100%)

Fetching: activerecord-3.2.8.gem (100%)

Fetching: activeresource-3.2.8.gem (100%)

Fetching: mime-types-1.19.gem (100%)

Fetching: polyglot-0.3.3.gem (100%)

Fetching: treetop-1.4.10.gem (100%)

Fetching: mail-2.4.4.gem (100%)

Fetching: actionmailer-3.2.8.gem (100%)

Fetching: rake-0.9.2.2.gem (100%)

Fetching: rack-ssl-1.3.2.gem (100%)

Fetching: thor-0.16.0.gem (100%)

Fetching: json-1.7.5.gem (100%)

Building native extensions.  This could take a while...

ERROR:  Error installing rails:

    ERROR: Failed to build gem native extension.



        /usr/bin/ruby1.9.1 extconf.rb

/usr/local/lib/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)

    from /usr/local/lib/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'

    from extconf.rb:1:in `<main>'





Gem files will remain installed in /usr/lib/ruby/gems/1.9.1/gems/json-1.7.5 for inspection.

Results logged to /usr/lib/ruby/gems/1.9.1/gems/json-1.7.5/ext/json/ext/generator/gem_make.out