Code for the question 77971921 on Stackoverflow

.gitignore

.docker-build.*

README.md

Gist for the code to Referencing environment variable in KubernetesPodOperator cmds

The images both exist as mwmahlberg/stackoverflow-77971921:entrypoint and mwmahlberg/stackoverflow-77971921:non-interactive in the according repo on dockerhub

Building the images

Entrypoint

docker build -t $YOURORG/$IMAGENAME:entrypoint -f Dockerfile.entrypoint

Non-interactive

docker build -t $YOURORG/$IMAGENAME:non-interactive -f Dockerfile.non-interactive

Makefile

Prerequisites

• git
• make (Duh!)
• docker
• A Dockerhub account should you want to push

Variables

Variable	description	default
DOCKERORG	The organization on dockerhub under which the image resides	mwmahlberg
DOCKERREPO	The repository for the image under $DOCKERORG	stackoverflow-77971921

You can set the variable per call via:

DOCKERORG="gcr.io/foobar" make

Targets

The Makefile has the following targets:

Target	description
all	builds both entrypoint and non-interactive
entrypoint	builds just the entrypoint variant
non-interactive	builds just the non-interactive variant
push	pushes all images of $DOCKERORG/$DOCKERREPO
clean	removes the temporary files
image-clean	removes the images.
all-clean	an alias for clean image-clean

Running the images

Entrypoint

docker run --rm  $YOURORG/$IMAGENAME:entrypoint

Non-interactive

docker run --rm $YOURORG/$IMAGENAME:non-interactive
Hello World

docker-entrypoint.sh

#!/bin/bash

# Exit immediately if a command exits with a non-zero status.
set -eo
env

Dockerfile.entrypoint

FROM alpine:3
RUN apk add --no-cache bash
ADD --chmod=755 docker-entrypoint.sh /docker-entrypoint.sh
ENV MY_VAR="Hello World"

ENTRYPOINT ["/docker-entrypoint.sh"]

Dockerfile.non-interactive

FROM mwmahlberg/stackoverflow-77971921:entrypoint
# The Environment variable MY_VAR is set in the parent image
ENTRYPOINT [ "/bin/bash","-c", "echo $MY_VAR"]

Makefile

DOCKERORG ?= mwmahlberg
DOCKERREPO ?= stackoverflow-77971921

TAGS=entrypoint non-interactive
GIT_HASH = $(shell git log --format="%h" -n 1)

.PHONY: all push clean image-clean entrypoint non-interactive all-clean

all: $(TAGS)

entrypoint: .docker-build.entrypoint
non-interactive: .docker-build.non-interactive

.docker-build.entrypoint: Dockerfile.entrypoint docker-entrypoint.sh
	docker buildx build --platform linux/amd64,linux/arm64 \
	-t $(DOCKERORG)/$(DOCKERREPO):entrypoint \
	-t $(DOCKERORG)/$(DOCKERREPO):entrypoint-git$(GIT_HASH) \
	-f $< .
	@touch $@

.docker-build.%: Dockerfile.%
	docker buildx build --platform linux/amd64,linux/arm64 \
	-t $(DOCKERORG)/$(DOCKERREPO):$* \
	-t $(DOCKERORG)/$(DOCKERREPO):$*-git$(GIT_HASH) \
	-f $< .
	@touch $@

push: $(patsubst %,.docker-build.%,$(TAGS))
	docker push -a $(DOCKERORG)/$(DOCKERREPO)

clean:
	$(RM) .docker-build.*

image-clean:
	docker rmi $(DOCKERORG)/$(DOCKERREPO):entrypoint
	docker rmi $(DOCKERORG)/$(DOCKERREPO):non-interactive
	docker rmi $(DOCKERORG)/$(DOCKERREPO):entrypoint-$(GIT_HASH)
	docker rmi $(DOCKERORG)/$(DOCKERREPO):non-interactive-$(GIT_HASH)

all-clean: clean image-clean