Getting Started Guide section 4.2: Could not find generator controller?

Hello. Brand new to Rails. Following along on the Getting Started guide, stuck on section 4.2 where upon entering:

$ rails generate controller welcome index

I receive:

Could not find generator controller

Everything seemed fine until this point. Any help is appreciated.

Which version of rails are you using?
rails -v

Also which operating system are you using and how did you install