if you’re running rails 3.0 or greater, you can also use
rails console production
production can of course be substituted with development or test (value is development by default)
Adding the option --sandbox makes it so that any changes you make to your database in the console will be rolled back after you exit
If this isn’t working for you, you may need to try
bundle exec rails console production
If you are actually trying to run the rails console on your production server, try googling “run rails console [your cloud hosting provider]” e.g. “run rails console heroku”
As of Rails 6 you need to use
RAILS_ENV=production bundle exec rails c
or
RAILS_ENV=production rails c
depending on your setup