Description
Is this a docs issue?
- My issue is about the documentation content or website
Type of issue
Information is incorrect
Description
On https://docs.docker.com/build/building/multi-platform/#prerequisites there is the following:
If you're using Docker Engine standalone and you need to build multi-platform images using emulation, you also need to install QEMU, see Install QEMU manually.
However, it turns out that non-Docker desktop buildkit itself will quietly try and do QEMU emulation (but as the name implies only at build time)! From https://github.com/moby/buildkit/blob/master/docs/multi-platform.md :
When your build needs to run a binary for architecture that is not supported natively by your host, it gets executed using a QEMU user-mode emulator. You do not need to set up QEMU manually in most cases.
I only know this because I spent some time scratching my head as to how a foreign architecture's build was succeeding on a machine that didn't have separate QEMU emulation configured (and yet actually running the built foreign architecture image was failing with exec format error as expected). At the time a Google search for "docker inbuilt qemu build" didn't turn up anything useful so hopefully creating this issue helps.
Location
https://docs.docker.com/build/building/multi-platform/
Suggestion
Please add a note that if buildkit XYZ or later is used then architecture emulation will automatically be tried using a built-in QEMU .