Docker Cross Compilation Example

This is a simple example of how to use Docker to cross compile an application.

Structure

• Dockerfile - The Dockerfile that defines the Docker image to be used in Cross compilation. This file must define all the environment variables, tools and dependencies needed for compilation. Of note, this Dockerfile is agnostic to the platform being compiled for. It is only concerned with the tools and dependencies needed for compilation.
• docker-compose.yml - The docker-compose file defines the platforms the Docker images are to be built for, the files loaded from the host to the containers created from these images, and the commands to be run.

The remainder of the repository is the source code for the application and the Makefile that defines the build process. This will vary from application to application.

Setting up docker buildx

The host machine must have docker buildx installed. Please consult https://github.com/docker/buildx for instructions on how to install this.

What is required is that your bootstrapped docker buildx instance has builders for each of the architectures you wish to compile for. In this example, we are compiling for amd64, arm64 and riscv64. To create these builds, we execute the following commands:

docker buildx create --use --name mybuild node-amd64
docker buildx create --append --name mybuild node-arm64
docker buildx create --append --name mybuild node-riscv64

Here a new builder, mybuild is created for amd64 then appended to with the arm64 and riscv64. The --use flag is used to set the builder as the default.

Usage

All you need to do to create the cross compiled binaries is run:

docker-compose up

For each architecture to be compiled to this command, by reading the docker-compose.yml file, will create an Image from the Dockerfile for that architecture, create a container from that image, mount the local source code into the container, then build and return the compiled product.