I’m running rvm and have ruby 1.9.2-p136 installed. Unfortunately, gem install ruby-debug throws all sorts of errors so I fumbled around and found this post:
http://dirk.net/2010/04/17/ruby-debug-with-ruby-19x-and-rails-3-on-rvm/
Which summarized a post by Mr. RVM himself:
https://rvm.beginrescueend.com/support/troubleshooting/
But I continued to receive errors when I ran the following command:
gem install ruby-debug19 -- --with-ruby-include="$rvm_src_path/$(rvm tools identifier)/"
I discovered I didn’t have the $rvm_src_path environment variable set anywheres! I fixed that problem by adding the following line to the end of my ~/.bashrc file:
export rvm_src_path="$rvm_path/src"