[root@ip-10-118-22-125 ~]# gem install berkshelf
Building native extensions.  This could take a while...
ERROR:  Error installing berkshelf:
	ERROR: Failed to build gem native extension.

    /usr/bin/ruby2.0 extconf.rb
mkmf.rb can't find header files for ruby at /usr/share/ruby/include/ruby.h


Gem files will remain installed in /usr/local/share/ruby/gems/2.0/gems/hitimes-1.2.1 for inspection.
Results logged to /usr/local/share/ruby/gems/2.0/gems/hitimes-1.2.1/ext/hitimes/c/gem_make.out