Version-Stamped Builds

Parameterize a build with ARG so CI stamps every image.

A intermediate Docker challenge worth 10 points. Solve it hands-on in a real Docker environment in your browser - no local setup, no fake shells.

The Challenge

Scenario: No hardcoded version numbers — the release pipeline injects them at build time. Requirements in /root/relay/README.md.

Tasks: write /root/relay/Dockerfile (base alpine:3.20) that:

• declares ARG BUILD_VERSION
• sets label org.app.version to it and writes it to /version.txt
• copies relay.sh to /usr/local/bin/relay.sh

Then build: docker build --build-arg BUILD_VERSION=2.5.1 -t relay:2.5.1 /root/relay

Commands to learn: ARG, LABEL, docker build --build-arg

Run check when done.