Leverage multi-CPU architecture support

Docker images can support multiple architectures, which means that a single image may contain variants for different architectures, and sometimes for different operating systems, such as Windows.

When running an image with multi-architecture support, docker will automatically select an image variant which matches your OS and architecture.

Most of the official images on Docker Hub provide a variety of architectures. For example, the busybox image supports amd64, arm32v5, arm32v6, arm32v7, arm64v8, i386, ppc64le, and s390x. When running this image on an x86_64 / amd64 machine, the x86_64 variant will be pulled and run, which can be seen from the output of the uname -a command that’s run inside the container:

$ docker run busybox uname -a

Linux 82ef1a0c07a2 4.9.125-linuxkit #1 SMP Fri Sep 7 08:20:28 UTC 2018 x86_64 GNU/Linux

Docker Desktop for Mac provides binfmt_misc multi-architecture support, which means you can run containers for different Linux architectures such as arm, mips, ppc64le, and even s390x.

This does not require any special configuration in the container itself as it uses qemu-static from the Docker for Mac VM. Because of this, you can run an ARM container, like the arm32v7 or ppc64le variants of the busybox image:

arm32v7 variant

$ docker run arm32v7/busybox uname -a

Linux 9e3873123d09 4.9.125-linuxkit #1 SMP Fri Sep 7 08:20:28 UTC 2018 armv7l GNU/Linux

ppc64le variant

$ docker run ppc64le/busybox uname -a

Linux 57a073cc4f10 4.9.125-linuxkit #1 SMP Fri Sep 7 08:20:28 UTC 2018 ppc64le GNU/Linux

Notice that this time, the uname -a output shows armv7l and ppc64le respectively.

Multi-architecture support makes it easy to build multi-architecture Docker images or experiment with ARM images and binaries from your Mac.