troubleshoot docker ENV

Dockerfile_alpine

FROM alpine:latest

ENV no_proxy internal.example.com,internal2.example.com
ENV NO_PROXY internal.example.com,internal2.example.com

RUN apk update && apk upgrade

Dockerfile_alpine_override

FROM base_alpine:latest

ENV no_proxy itworks
ENV NO_PROXY itworks

RUN echo ${no_proxy}
RUN echo ${NO_PROXY}

Dockerfile_ubuntu

FROM ubuntu:latest

ENV no_proxy internal.example.com,internal2.example.com
ENV NO_PROXY internal.example.com,internal2.example.com

RUN apt update && apt upgrade -y

Dockerfile_ubuntu_override

FROM base_ubuntu:latest

ENV no_proxy itworks
ENV NO_PROXY itworks

RUN echo ${no_proxy}
RUN echo ${NO_PROXY}

run.sh

#!/bin/zsh
export DOCKER_CLI_HINTS=false

# Build some base images
docker build . -f Dockerfile_ubuntu -t base_ubuntu
docker build . -f Dockerfile_alpine -t base_alpine

# Build the secondary images
docker build . -f Dockerfile_ubuntu_override -t overrider_ubuntu
docker build . -f Dockerfile_alpine_override -t overrider_alpine

# Test the env override

on_ubuntu=$(docker run overrider_ubuntu env | grep -i proxy)
on_alpine=$(docker run overrider_alpine env | grep -i proxy)

echo "on ubuntu the env var is: \n$on_ubuntu"
echo "on alpine the env var is: \n$on_alpine"