Simplifying Docker Multiplatform Builds with Buildx

In this post, we’re exploring a tool in the Docker universe, Buildx. Docker Buildx simplifies image building for different platforms (like AMD64, ARM64, etc.)

What’s the Issue with Multiplatform Docker Images?

Building Docker images that work across different architectures, such as Intel’s x86_64 and ARM’s AArch64, can be a challenging task. Typically, creating a Docker image that can run on various hardware platforms requires setting up a complicated build process for each one, which can lead to additional work and a greater possibility of errors.

Enter Docker Buildx

Buildx is a plugin for Docker CLI that makes it easier to create images for multiple platforms. It uses the advanced features and capabilities of Docker’s BuildKit, which are not available in the standard Docker build. One of the key benefits of Buildx is its seamless ability to build and run images across different platforms. This makes it a powerful tool for developers who need to create images that can run on a variety of systems.

How Does Buildx Solve the Problem?

1. Simplified Build Process: With Buildx, you don’t need separate build processes for each platform. You can create a single Dockerfile and Buildx will handle the rest, building images for AMD64, ARM64, and more, all at once.
2. Emulation Support: Buildx uses QEMU, an open-source emulator, allowing you to build images for platforms different from your host machine. This means you can build ARM images on an AMD64 machine.
3. Efficiency and Speed: Buildx optimizes the use of cache, reducing build times and resource usage. This efficiency is a game-changer for developers working with multiarchitecture images.

Let’s create a simple Go example and see how Docker Buildx works.

First, let’s create a simple main Go application file. This application will just print “hello docker buildx” to the console.

Next, we need a Dockerfile to containerize the Go application:

Now, let’s use Docker Buildx to build this application for both AMD64 and ARM64 architectures.

First, create a new builder instance that enables building for multiple platforms.

docker buildx create --name mybuilder --use

Start the builder instance.

docker buildx inspect --bootstrap

Use the docker buildx, build command to build and push the image to Docker Hub (or another registry).

docker buildx build --platform linux/amd64,linux/arm64 -t <username/repo:tag> . --push

After the build completes, you can check the image manifest to verify that it has been built for multiple platforms.

docker manifest inspect <username/repo:tag>

Resource:

Docker: Up & Running, 3rd Edition