heroku run rails db:migrate This tells Heroku to run your migrations on its database, like running rails db:migrate locally. Heroku's database is separate from the one on your computer, which means it needs to be updated every time you make changes to the structure of your database.
So, to start a new Rails 5 app, we need to do the following. First, make sure you have installed and are using Ruby 2.3.0. Then: $ gem install rails --pre Successfully installed rails-5.0.0.beta3 Parsing documentation for rails-5.0.0.beta3 Done installing documentation for rails after 1 seconds 1 gem installed