In my blog post Moving from Linux to macOS, I described my motivation for moving to macOS. One consequence of this move is that my CPU architecture changed from x86-64 to ARM.
Requirements#
- Docker
- buildx (included in Docker Desktop for Windows and macOS)
- Optional: Github and Dockerhub account if you want to automatically build and publish your image
Dockerfile#
Of course, you must build your Docker image upon a base image that supports all target platforms. With the following snippet Docker will automatically use the right architecture of the base image.
ARG ARCH=
FROM ${ARCH}debian:stable-slim
How to download applications for the specific architecture? There is a list of variables that are automatically set when building images with buildkit (the approach in this post). We can use the relevant variables to determine the platform. These variables must be exposed at the top of your Dockerfile before you can use them in RUN sections.
ARG TARGETOS # operating system, e.g. linux
ARG TARGETARCH # CPU architecture, e.g. amd64
ARG TARGETVARIANT # e.g. v8
RUN curl -sLo /usr/local/bin/yq https://github.com/mikefarah/yq/releases/download/${YQ_VERSION}/yq_linux_${TARGETARCH}
Building#
Building is almost as easy as your usual build. Just add your target platform(s) to the command. Refer to build multi platform images for more details.
docker buildx build --platform linux/amd64 -t test .
Automatic builds on Github#
If you want to automatically build (and push) your image via Github actions there is workflow available. Refer to my repo’s workflow.
