Rails 3: Could Not Find Generator devise:install

Something I keep forgetting about, is how Rails 3 treats gems. Any gem you want to use (in this case it was devise) needs to be setup in the Gemfile.

If you try to run Devise’s installation: rails generate devise:install you’ll get Could not find generator devise:install.

What happens is rails doesn’t detect that the devise gem is needed, and therefore doesn’t load it. All you’ve got to do is open the Gemfile for your project and add the following line, where the gem version matches what you are currently using:

gem 'devise', '1.4.7'

Run the installation command again and you should be good to go!