Set Dockerfile frontend via the syntax directive

[atc0005]

Overview

Current versions of Docker (and from what I can tell Podman) support using the syntax directive to specify a desired build image for building images. If you don't use this directive then the built-in or default Dockerfile frontend is used.

To retain existing (overall) behavior while allowing new features adding # syntax=docker/dockerfile:1 as the first line in a Dockerfile is the current recommended practice.

I've not researched this sufficiently to determine if there are any downsides.

References

• https://www.bretfisher.com/cloud-native-devops-36/
• https://docs.docker.com/build/dockerfile/frontend/
• https://docs.docker.com/engine/reference/builder/#syntax
• https://hub.docker.com/r/docker/dockerfile/
• https://matduggan.com/the-hunt-for-a-better-dockerfile/
• https://pythonspeed.com/articles/podman-buildkit/