Then deleting `lib/rails/fly.rake’ and then running:
bundle add dockerfile-rails --optimistic --group development
bin/rails generate dockerfile
… and accepting the changes.
That will bring you up to date with the latest changes to flyctl launch. You are also encouraged to read Dockerfiles and fly.toml · Fly Docs to see if there are any suggestions that you might want to take advantage of.
If you have a heavily customized Dockerfile or have another reason why you don’t want to accept the Dockerfile changes, create a two line script that runs your current release command followed by your current CMD from the Dockerfile, and then change the CMD to run your script.
For non-Rails applications with a single server in a single region, the same recommendations apply other than not having the benefit of a script.
Should not have affected volumes, but Rails’s new conventions do differ from fly’s previous ones in that the app is at /rails instead of /app, and the port is now 3000 rather than 8080. Were you mounting the volume into the /app directory?