DevOps Articles

Introduction to heredocs in Dockerfiles

Guest post by Docker Community Member Justin Chadell. In this post, I’ll cover the basics of what these heredocs are, and more importantly what you can use them for, and how to get started with them!

Essentially, it’s the next generation builder for docker images, neatly separate from the rest of the main docker runtime; you can use it for building docker images, or images for other OCI runtimes.

You can enable it locally by setting the environment variable DOCKER_BUILDKIT=1 when performing your docker build, or switch to using the new(ish) docker buildx command.

With buildkit properly setup, you can create a new Dockerfile: at the top of this file, we need to include a #syntax= directive.