Multi-stage builds concept in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a multi-stage build in Docker?

A multi-stage build is a Docker feature that lets you use multiple FROM statements in one Dockerfile. It helps create smaller images by copying only the needed parts from earlier stages to the final image.

beginner

Why use multi-stage builds?

Multi-stage builds reduce the final image size and improve security by excluding build tools and temporary files from the final image.

intermediate

How do you copy files from one stage to another in a multi-stage build?

You use the COPY --from= command to copy files from a previous build stage to the current stage.

intermediate

Give an example of a simple multi-stage Dockerfile.

Example: FROM golang:1.20 AS builder WORKDIR /app COPY . . RUN go build -o myapp FROM alpine:latest COPY --from=builder /app/myapp /myapp CMD ["/myapp"]

beginner

What happens if you don’t use multi-stage builds for compiled applications?

Without multi-stage builds, the final image may include unnecessary build tools and source files, making it larger and less secure.

What is the main benefit of using multi-stage builds in Docker?

A More layers in the image

B Faster container startup time

C Smaller final image size

D Automatic updates of base images

Multi-stage builds help create smaller images by copying only necessary files to the final image.

How do you specify which stage to copy files from in a multi-stage build?

A COPY --from=<stage-name>

B COPY --stage=<stage-name>

C COPY --source=<stage-name>

D COPY --use=<stage-name>

The correct syntax to copy files from a previous stage is COPY --from=.

Which Dockerfile instruction starts a new build stage?

A RUN

B CMD

C COPY

D FROM

Each FROM instruction starts a new build stage in a multi-stage Dockerfile.

What is a common use case for multi-stage builds?

A Building and packaging compiled applications

B Running multiple containers at once

C Creating network bridges

D Managing container logs

Multi-stage builds are often used to compile code in one stage and copy the final binary to a smaller image.

If you want to keep build tools out of the final image, what should you do?

A Use a single-stage build

B Use multi-stage builds

C Install tools in the final image

D Use a larger base image

Multi-stage builds allow you to exclude build tools from the final image by separating build and runtime stages.

Explain how multi-stage builds help reduce Docker image size and improve security.

Think about separating build environment from runtime environment.

Describe the steps to create a multi-stage Dockerfile for a compiled application.

Focus on build and final stages.