SAP BTP, Kyma runtime is SAP's fully managed commercial kubernetes offering, part of SAP Business Technology Platform. It is often bundled with SAP Commerce Cloud and nowadays is becoming an extensibility runtime of choice.
The docker files used in the function build are stored as config maps in a kyma cluster namespaces. Goto your cluster to look them up.
Building a custom image.
In order the build a custom image first you need to clone the project kyma github repository:
gh repo clone kyma-project/kyma
add your Dockerfile, build the custom image and push it
to an internet facing docker repository
cp Dockerfile Dockerfile.custom.nodejs16
edit your Dockerfile.custom.nodejs16 then save it
and build your custom image
docker build --platform amd64 -t <docker_id>/<docker_repo>:bullseye-slim16 -f ./Dockerfile.custom.nodejs16 .
You also need to make a decision about a new base nodejs16 image. That's an important decision as you are entirely liable/responsible for this choice and the custom image that will be built based upon it.
Next, you can create a custom function base image using a custom Dockerfile.custom.nodejs16definition.
Last but not least, you shall need to publish the image to a public and internet facing docker repository.
For instance, let's say the new nodejs base image is node:16.19.0-bullseye-slim and that we are going to add a bunch of linux libraries to accommodate for any specific runtime dependencies, as follows: