Ship the Tool, Not the Toolchain

Convert a bloated single-stage build to multi-stage.

A advanced Docker challenge worth 20 points. Solve it hands-on in a real Docker environment in your browser - no local setup, no fake shells.

The Challenge

Scenario: tool:v1 works, but ships its whole 30MB build toolchain for an app that is one shell script.

Tasks: rewrite /root/tool/Dockerfile as a multi-stage build:

• stage 1 (FROM alpine:3.20 AS build): toolchain + "compile", exactly like today
• stage 2 (FROM alpine:3.20): COPY --from=build only /usr/local/bin/app
• Build as tool:v2: same behavior (docker run --rm tool:v2 app → tool ok), ≥25MB smaller, no /opt/toolchain.bin inside

Commands to learn: multi-stage FROM … AS, COPY --from

Run check when done.