Build a Container Image for Another Platform Using QEMU Emulation

In this challenge, you will build a container image for the arm64 architecture on an amd64 host machine using QEMU user-space emulation.

Explore the application

The ~/app/ directory contains a simple Node.js web application and a pre-written Dockerfile. Take a moment to explore the code and the Dockerfile before you begin:

ls ~/app/

cat ~/app/Dockerfile

If you use the standard docker build command with the provided Dockerfile, it will produce an image for the host's native architecture (amd64):

docker build -t test-native ~/app/

The below command should print x64, confirming the image is built for the host's architecture:

docker run --rm test-native node -e "console.log(process.arch)"

The task

Your goal is to build the same application as an arm64 image instead:

1. Enable QEMU user-space emulation for the arm64 architecture on this machine.
2. Build the Docker image for the linux/arm64 platform, tagging it as my-app:v1.0.0.
3. Make sure the containerized application starts and responds correctly on port 3000.

You can verify the image architecture at any point:

docker image inspect my-app:v1.0.0 | jq '.[0].Architecture'

docker run --rm test-native node -e "console.log(process.arch)"

Hint 1

Docker can't natively execute binaries compiled for a different CPU architecture. To cross-build, you need to register QEMU user-space emulators with the kernel using the binfmt_misc mechanism.

A popular way to do this in a Docker environment is by running a special privileged container. Check out the official Docker documentation and the tonistiigi/binfmt project for more details.

docker run -p 3000:3000 my-app:v1.0.0