anyarch-docker-guest

This README summarizes a method for running docker guest systems of arbitrary architectures on a given host system. It is largely based on the approaches described in [1] and [2]. In brief, the method works by running syscalls issued in the docker guest system through QEMU, which makes the interface between host and guest system. Interested readers who would like to learn how the method works in more detail are referred to the aforementioned references. The main contribution of this repository is to provide an updated patch for QEMU that brings the original work of Petros Angelatos [3] in line with current versions of the emulator. The patch has been submitted for inclusion in QEMU and can be tracked in [5].

Edit 2022/02/24: Patch bumped to QEMU-6.2.0.

Goal

The following steps describe how to run a guest docker container based on Debian AArch64 [4] on an x86 host. The choice of architecture is rather arbitrary (as long as QEMU supports it, any guest/host architecture should work).

Steps

1. Compile a patched static QEMU emulator

git clone git://git.qemu.org/qemu.git
git checkout v6.2.0
cd qemu
git apply ../v5-linux-user-add-option-to-intercept-execve-syscalls.diff
./configure --static --target-list=aarch64-linux-user
make

This will create a static QEMU emulator, build/qemu-aarch64, patched with a new option, --execve, that can be used to issue the recursive emulated execution of a process and its children.

Next, we copy the static binary to outside the QEMU tree.

cp build/qemu-aarch64 ..

2. Create a docker image for the architecture you wish to emulate

docker build -t debian-arm64v8 .

Note that the Dockerfile included in this repository purposefully updates the base Debian image, and the commands involved to accomplish the update already run emulated.

Next, simply start a container based on the image created and test that everything works.

$ docker run -it --rm debian-arm64v8
root@8b88909fa3f1:/# uname -m
aarch64
root@8b88909fa3f1:/# 

References

[1] https://www.balena.io/blog/building-arm-containers-on-any-x86-machine-even-dockerhub/
[2] https://blog.cloudflare.com/porting-our-software-to-arm64/
[3] https://patchwork.ozlabs.org/project/qemu-devel/patch/1455515507-26877-1-git-send-email-petrosagg@resin.io/
[4] https://hub.docker.com/r/arm64v8/debian/
[5] https://patchew.org/QEMU/20200730160106.16613-1-rj.bcjesus@gmail.com/