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

<table class="tg"> <tr> <th class="tg-yw4l">Platform</th> <th class="tg-yw4l">Number of Instance</th> <th class="tg-yw4l">Reading Time</th> </tr> <tr> <td class="tg-yw4l"> Play with Docker</td> <td class="tg-yw4l">1</td> <td class="tg-yw4l">5 min</td> </tr> </table>

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

Contributor

Savio Mathew

Lab #10: VOLUME instruction