Ubuntu を使用して " bundle install
" を実行して Rails 環境をセットアップすると、JSON gem のインストール中にエラーがスローされます。
Installing json (1.7.3) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/usr/bin/ruby1.9.1 extconf.rb
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)
from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from extconf.rb:1:in `<main>'
Gem files will remain installed in /home/danny/.bundler/tmp/2040/gems/json-1.7.3 for inspection.
Results logged to /home/danny/.bundler/tmp/2040/gems/json-1.7.3/ext/json/ext/parser/gem_make.out
An error occured while installing json (1.7.3), and Bundler cannot continue.
Make sure that `gem install json -v '1.7.3'` succeeds before bundling.
JSON 1.7.3 gem のみをインストールしようとすると、エラーも表示されます。
Building native extensions. This could take a while...
ERROR: Error installing json:
ERROR: Failed to build gem native extension.
/usr/bin/ruby1.9.1 extconf.rb
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)
from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from extconf.rb:1:in `<main>'
Gem files will remain installed in /var/lib/gems/1.9.1/gems/json-1.7.3 for inspection.
Results logged to /var/lib/gems/1.9.1/gems/json-1.7.3/ext/json/ext/parser/gem_make.out
RVM をインストールし、Ruby 1.9.3 を実行しています。JSON gem をインストールできないのはなぜですか?