The purpose of this container is to demonstrate how to read environment variables and write them to a directory. When deploying a container application (e.g. Angular application), at runtime, you might have to read environment variables to configure the application.

This container uses supervisor to achieve the intended effect as an attempt to be a disciplined approach. For example, you could create a shell script and use ENTRYPOINT or CMD to execute that shell script at startup. However, how would you put multiple services into the foreground? In this container, supervisor calls the doit.sh script to read the environment variables, and then writes them to /usr/share/nginx/html/env.json; the service is called setupenv. Finally, the supervisor service called nginx starts nginx in non-daemon mode.

Image

Build it.

./build.sh

Run it.

docker run -it -p 80:80 nginx-env:local

Observe it.

docker exec -it [CONTAINER_ID] cat /usr/share/nginx/html/env.json
docker exec -it [CONTAINER_ID] /bin/bash

Check out John Henry Holland.

@misc{oneoffcoder_nginx_env_2019, 
title={Docker container showing how to read environment variables}, 
url={https://github.com/oneoffcoder/docker-containers/tree/master/nginx-env}, 
journal={GitHub},
author={One-Off Coder}, 
year={2019}, 
month={Jul}}