While you would usually rest on the shoulders of giant, configuring, or re combining existing buildpacks, let's go through the exercise of creating a (almost) complete buildpack (including a builder, and a stack).
I was greatly inspired by the official CNCF buildpacks samples repository.
You'll need to begin with a stack : basically some run and some build image that can share a base image.
The important bit ? This label:
LABEL io.buildpacks.stack.id=net.dahanne.stack.anthony
Once they're built, you can move on to the next step.
You could create at the mininum 1 buildpack, but in this example, we have several buildpacks to showcase the ordering.
Each buildpack (except meta-paketo-adoptopenjdk that is a meta buildpack composing several others) comes with a bin folder and its detact and build script.
Also, they each come with a buildpack.toml and a package.toml
Pay attention to the version, name, and also on which stack it can run; of course those builpacks can all run on the stack created previously.
The builder is the piece of metadata that glues the buildpacks and their stack(s) together.
In this example builder we are composing and ordering 3 buildpacks that we created previously and the stack we created previously.
Finally, let's try this simple builder on a project!
Among the 3 buildpacks, the simple-html-page buildpack can detect an index.html page and can build an image with a very trivial webserver to serve it !