I recently went to create a new Rake task under /lib/tasks in a Rails application I’m working on. I didn’t understand why the rake tasks weren’t showing when I would run rake -T from the command line.

When I’d try to run the task itself I would get a ‘Don’t know how to build task’ error.

I just realized that I was naming my task file with the ‘.rb’ extension, and not ‘.rake’. Doh!