Lab #9: ENV instruction
The ENV instruction in Dockerfile sets the environment variable for your container when you start. The default value can be overridden by passing --env <key>=<value> when you start the container.
Pre-requisite:
Tested Infrastructure
| Platform | Number of Instance | Reading Time |
|---|---|---|
| Play with Docker | 1 | 5 min |
Pre-requisite
- Create an account with DockerHub
- Open PWD Platform on your browser
- Click on Add New Instance on the left side of the screen to bring up Alpine OS instance on the right side
Assignment
- Writing a Dockerfile with ENV instruction
- Building Docker Image
- Running container env:v1
- Override existing env while running container
Writing a Dockerfile with ENV instruction
Dockerfile
FROM alpine:3.9.3
LABEL maintainer="Collabnix"
ENV WELCOME_MESSAGE="Welcome to Docker World"
CMD ["sh", "-c", "echo $WELCOME_MESSAGE"]
Building Docker Image
$ docker build -t env:v1 .
Running container env:v1
$ docker container run env:v1
Welcome to Docker World
Override existing env while running container
$ docker container run --env WELCOME_MESSAGE="Welcome to Docker Workshop" env:v1
Welcome to Docker Workshop