Where can I see the version of qemu that Docker Desktop is using?

Docker Desktop
1

Windows Docker Desktop

PS > wsl -d docker-desktop           
docker-desktop:/tmp/docker-desktop-root/run/desktop/mnt/host/c# qemu-system-x86_64 --version
-sh: qemu-system-x86_64: not found
docker-desktop:/tmp/docker-desktop-root/run/desktop/mnt/host/c# qemu
-sh: qemu: not found
2

Why do you think it uses qemu?

Normally Docker Desktop on Windows just uses a VM. qemu is for emulating different hardware architecture. You can use it on Mac with ARM chip to run x86 binaries.

3

I’m not on Windows now, but this should work:

docker run --rm -it --privileged --pid host ubuntu nsenter --all -t 1 qemu-x86_64 --version

My output on Mac:

qemu-x86_64 version 8.1.5 (v8.1.5)
Copyright (c) 2003-2023 Fabrice Bellard and the QEMU Project developer

Explanation: Since the Docker daemon is running in a containr, qemu does not have to be in the PATH in the WSL distro directly. The command I shared runs the qemu command to get the version inside the container in which the Docker daemon is running.

It is, but it is needed in Docker Desktop to be able to emulate arm on amd as well, so it is in Docker Desktop on all platforms. It is of course not the same as the one on macOS which was the legacy virtualization method to run Docker Desktop’s VM itself.

4

Yeah, I tried that:

docker run --rm -it --pid=host --privileged ubuntu:22.04 nsenter --all -t 1 qemu-arm --version
qemu-arm version 8.1.5 (v8.1.5)

but I wasn’t sure if this was the relevant version.
Since when building from amd to arm I get the error: qemu: uncaught target signal 11 (Segmentation fault) - core dumped windwos.
This sounds like nonsense. I gave wsl 40gb of RAM and 6 process cores, so suspicious of how Docker allocates resources to qemu.
I followed the standard recommendations from the internet to update qemu, supposedly the version is old. The command above shows the version, but the error still remained.

Now with the same build from amd to arm there is no qemu error, now just:

 > [base  2/17] RUN apt-get upgrade    && apt-get update    && apt-get install -y    g++    gcc    cmake    make    git    python3    libgl1-mesa-dev    libdrm-dev    libgles2-mesa-dev    libboost-all-dev    golang-go    wget    iputils-ping:
0.284 exec /bin/sh: no such file or directory

apparently this happened after another attempt to update qemu with some docker run command.

By the way, I’m building this:

FROM ubuntu:22.04 AS base

ARG DEBIAN_FRONTEND=noninteractive

RUN apt-get upgrade \
   && apt-get update \
   && apt-get install -y \ 
   g++ \ 
   gcc \ 
   cmake \ 
   make \ 
   git \
   python3 \
   libgl1-mesa-dev \
   libdrm-dev \
   libgles2-mesa-dev \
   libboost-all-dev \
   golang-go \
   wget \
   iputils-ping
5

Since Qemu is in the virtualk machine, it will be as much resources as the VM has. On Windows, in case of WSL2, you can increase the resources of WSL which cannot be done through Docker Desktop.

https://learn.microsoft.com/en-us/windows/wsl/wsl-config#main-wsl-settings

But Segmentation fault does not sound like a resource allocation issue. If you think the version of Qemu installed in Docker Desktop has a bug, you can report it on GitHub

If it can be fixed with an updated version, the developers can do it. If anything needs to be done with the virtual machine, that means it needs to be done with WSL so that means the developers at Microsoft, but I’m sure Docker can contact them if needed.