Introduction

Docker has revolutionized the way we package and deploy applications, making it easier to ensure consistency across different environments. However, when it comes to building Docker images for multiple architectures, such as linux/amd64 and linux/arm64, there are some challenges to overcome. In this blog post, we’ll explore how to build Docker images that work seamlessly on both x86-64 and ARM64 architectures.

The Rise of ARM-based Chips

In recent years, ARM-based chips have gained significant popularity in the computing industry. Companies like Amazon Web Services (AWS) have introduced ARM-based instances, such as the Graviton series, which offer cost savings and improved performance compared to traditional x86-64 instances.

ARM-based chips, like AWS Graviton and Apple’s M1, are designed to deliver high performance while consuming less power. This makes them an attractive option for cloud providers and users looking to optimize costs and reduce their carbon footprint. As a result, more and more applications are being deployed on ARM-based infrastructure.

def hello_world():
    print("Hello, World!")

Building Docker Images: The Regular Way

Traditionally, building a Docker image involves creating a Dockerfile that defines the steps to build your application. Here’s a simple example:

FROM node:14

WORKDIR /app

COPY package\*.json ./
RUN npm install

COPY . .

CMD ["npm", "start"]

To build the image, you run the following command:

docker build -t my-app .

This approach works well for a single architecture, but what happens when you need to support multiple architectures?

The Problem with Single-Architecture Images

When you build a Docker image using the regular approach, it is compiled specifically for the architecture of the machine you are building on. For example, if you build the image on a machine with an x86-64 (AMD64) processor, the resulting image will only work on systems with the same architecture.

This becomes a problem when you want to run your application on a different architecture, such as ARM64-based processors like AWS Graviton or Apple’s M1 chip. If you try to run an image built for x86-64 on an ARM64 system, you’ll encounter compatibility issues, and your application won’t run.

Building Multi-Architecture Docker Images

To overcome this limitation and create Docker images that work on both x86-64 and ARM64 architectures, we need to use a tool called buildx. buildx is an experimental feature in Docker that allows you to build images for multiple platforms simultaneously.

Here’s how you can build a multi-architecture Docker image:

  1. Enable Docker experimental features:
   export DOCKER_CLI_EXPERIMENTAL=enabled
  1. Create a new builder instance:
   docker buildx create --name mybuilder
   docker buildx use mybuilder
   docker buildx inspect --bootstrap
  1. Build the multi-architecture image
   docker buildx build --platform linux/amd64,linux/arm64 -t my-app:latest .

This command builds the image for both x86-64 and ARM64 architectures and tags it as my-app:latest .

  1. Push the image to a registry
   docker buildx build --platform linux/amd64,linux/arm64 -t my-app:latest --push .

By adding the --push flag, the built images are automatically pushed to the configured registry.

Conclusion

Building Docker images for multiple architectures is essential to ensure compatibility and portability across different systems, especially with the growing adoption of ARM-based chips like AWS Graviton and Apple’s M1. These chips offer cost savings and improved performance, making them an attractive option for many organizations.

By leveraging the buildx tool, you can easily create images that work seamlessly on both x86-64 and ARM64 architectures. This allows you to deploy your applications on a wider range of platforms and take advantage of the benefits offered by ARM-based infrastructure.

Happy Building!