Error installing gems that use native extensions on Ubuntu, Ruby 1.9.2 via RVM

Question

I get an error while trying to install the ffi gem:

~ - 16:54>gem i ffi
Building native extensions.  This could take a while...
ERROR:  Error installing f         


        

Answer 1

The installer attempts to run rake but fails when it isn't found:

can't find gem rake ([">= 0"]) with executable rake (Gem::GemNotFoundException)

You need to install the rake gem: gem install rake.