GitHub Codespaces: how to set x86_64, AMD64, ARM64 platform? – Docker

First, the question: is there a way to choose the platform (e.g. x86_64, AMD64, ARM64) for a GitHub Codespace?

Here’s what I’ve found so far:

Attempt 1 (not working):

From within GitHub.com, you can choose the "machine" for a Codespace, but the only options are RAM and disk size.

Attempt 2 (EDIT: not working): devcontainer.json

When you create a Codespace, you can specify options by creating a top-level .devcontainer folder with two files: devcontainer.json and Dockerfile

Here you can customize runtimes, installed packages, etc., but the docs don’t say anything about determining architecture…

…however, the VSCode docs for devcontainer.json has a runArgs option, which "accepts Docker CLI arguments"…

and the Docker CLI docs on –platform say you should be able to pass --platform linux/amd64 or --platform linux/arm64, but…

When I tried this, the Codespace would just hang, never finishing building.

Attempt 3 (in progress): specify in Dockerfile

This route seems the most promising, but it’s all new to me (containerization, codespaces, docker). It’s possible that Attempts 2 and 3 work in conjunction with one another. At this point, though, there are too many new moving pieces, and I need outside help.

1. Does GitHub Codespaces support this?
2. Would you pass it in the Dockerfile or devcontainer.json? How?
3. How would you verify this, anyway? [Solved: dpkg --print-architecture or uname -a]
4. For Windows, presumably you’d need a license (I didn’t see anything on GitHub about pre-licensed codespaces) — but that might be out of scope for the question.

References:
https://code.visualstudio.com/docs/remote/devcontainerjson-reference
https://docs.docker.com/engine/reference/commandline/run/
https://docs.docker.com/engine/reference/builder/
https://docs.docker.com/desktop/multi-arch/
https://docs.docker.com/buildx/working-with-buildx/