Going through the book in 2026 is a bit challenging as all the tech moves on as time passes.
I started by trying to just select the minimum level of ruby that would allow me to proceed forward. In this case ruby-3.4 (as of Mar 2026).

I’ve now gotten to writing the Dockerfile and since one is autogenerated in modern Rails I decided to delete the auto-generated Dockerfile and proceed from the book from there.

Unfortunately I got blocked on page 25

docker run -p 3000:3000 f1f5e523aaef \ bin/rails s -b 0.0.0.0
docker: Error response from daemon: failed to create task for container: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: error during container init: exec: " bin/rails": stat  bin/rails: no such file or directory

Run 'docker run --help' for more information

I’ll keep working at it. I might start over and use the most recent version of ruby instead of minimum level to get it to run to see if that solves the problem. Interested in any thoughts folks have about this error though.