无法加载此类文件 - mkmf（LoadError）

Question

Using rbenv, runnng bundle install, and getting an error installing Json 1.8.1.

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>'

Tried installing ruby-dev via apt (not sure that will help anyway, as ruby was installed via rbenv)

stuff that may help?

$ which gem
/home/ubuntu/.rbenv/shims/gem
$ which ruby
/home/ubuntu/.rbenv/shims/ruby
$ locate mkmf
/home/ubuntu/.rbenv/versions/1.9.3-p484/lib/ruby/1.9.1/mkmf.rb
/home/ubuntu/.rbenv/versions/1.9.3-p484/share/ri/1.9.1/system/Object/mkmf-i.ri
/usr/local/rvm/gems/ruby-2.2.1/extensions/x86_64-linux/2.2.0/nokogiri-1.6.6.2/mkmf.log
/usr/local/rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/mkmf.rb

Answer 1

Based on your locate command, you have mkmf in rvm and in ubuntu's home diretory, but not on the system, and you're explicitly using the system's ruby (and not rbenv or rvm) to run the extconf.rb. Either run a ruby from one of the environments you have mkmf in, or install the ruby-dev package on the system.