Docker buildx

Jun 11, 2024 • Cheatsheet/Docker • 2 min read

To build multi-architecture Docker images for both ARM and AMD64 architectures, you can use Docker's Buildx feature. Buildx allows you to build images for multiple platforms with a single command.

Here are the steps to build Docker images for ARM and AMD64 architectures:

Step-by-Step Guide

Install Docker Buildx: Docker Buildx is included in Docker versions 19.03 and later. You can check your Docker version and install or update Docker if necessary.
```
docker --version
```
Create and Use a Buildx Builder: Create a new builder instance and switch to it.
```
docker buildx create --use
```
Inspect the Builder: Ensure that your builder supports the required platforms.
```
docker buildx inspect --bootstrap
```
You should see support for multiple platforms like linux/amd64 and linux/arm64.
Build the Multi-Architecture Image: Use the docker buildx build command with the --platform flag to specify the target architectures. Use the --push flag to push the built image to a Docker registry, or use the --load flag to load it into your local Docker daemon (only works for single architecture builds).
```
docker buildx build --platform linux/amd64,linux/arm64 -t <your-username>/<image-name>:<tag> --push .
```
Replace <your-username>, <image-name>, and <tag> with your Docker Hub username, desired image name, and tag.

Example

Here’s an example of building a simple multi-architecture Docker image for both ARM64 and AMD64 architectures:

Dockerfile: Create a Dockerfile for your application. For this example, we'll use a simple Dockerfile:

# syntax=docker/dockerfile:1
FROM alpine:3.14
COPY . /app
WORKDIR /app
RUN apk add --no-cache python3 py3-pip
CMD ["python3", "app.py"]

Build and Push: Navigate to the directory containing your Dockerfile and run the following command:

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

Notes

Ensure you are logged in to Docker Hub (or your preferred Docker registry) before running the build command:
```
docker login
```
If you encounter any issues, make sure that QEMU is installed on your system for emulating the ARM architecture on x86 systems. Docker Buildx should handle this automatically with the --bootstrap flag, but you can install it manually if needed:
```
docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
```

By following these steps, you can build and push multi-architecture Docker images suitable for both ARM and AMD64 platforms.