This blog posts explains how to get rid of the Undefined method error when migration ActiveStorage from Rails 6.0 to 6.1.

Undefined method `name’ for nil:NilClass in AddServiceNameToActiveStorageBlobs

You may have recently upgraded to Rails 6.1 and generated the ActiveStorage migrations to migrate to the new ActiveStorage version where multiple storage providers can be used simultaneously.

If you get the following error:

NoMethodError: undefined method `name' for nil:NilClass
app/db/migrate/20201214195719_add_service_name_to_active_storage_blobs.active_storage.rb:7:in `up'

Make sure you have an ActiveStorage service defined in your environments configuration file. This can either be environments/development.rb, environments/test.rb or environments/production.rb. Make also sure it is not commented out:

screenshot of config lines in production.rb