chef で Failed to build gem native extension

CentOS

以下のエラーが発生。

ERROR:  Error installing chef:
	ERROR: Failed to build gem native extension.

/usr/bin/ruby extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/ruby.h


Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/yajl-ruby-1.2.1 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/yajl-ruby-1.2.1/ext/yajl/gem_make.out

ruby-devel がないからでした。

# yum -y install ruby-devel

でOK。