My config toml has
[build]
dockerfile = "Containerfile.foo"
Relying on config fails:
$ flyctl machine run . -c fly-foo.toml --name bar --schedule hourly
Error app does not have a Dockerfile or buildpacks configured. See https://fly.io/docs/reference/configuration/#the-build-section
Specifying the containerfile explicitly works:
$ flyctl machine run . -c fly-foo.toml --dockerfile Containerfile.foo --name bar --schedule hourly