Guix System on WSL

If you know what both WSL and Guix System, your first reaction might be a bit of a surprise. WSL is Microsoft’s Linux subsystem for Windows, a proprietary operating system that embeds candy crush ads in the start bar that is less stable than its alternatives, and everything it stands for screams corporate, while GNU Guix System is a free OS trying to be as pure as possible, both in terms of being immutable and also avoiding non-free software (not just proprietary, but also non-free source-available software). Guix is the antithesis of Windows.

While the fans of the two generally might not overlap, I use both, and I do like a lot of features Guile and Guix provide like the repl interaction through Emacs (with Geiser), Guix shells, Guix containers, Guix pack ing docker containers or rpm or deb files, and many more things. Windows is convenient and I use it for Work. While the bad rep Windows gets is fully justified, it has improved drastically since Microsoft’s early days (when Linux was not their favorite), and now it has a nice terminal, a decent package manager, and some sort of tiling.

Guix on WSL

If your attention span is as bad as mine and you need a quick TL;DR for building the image on a machien with guix, here’s the command:

guix system image -t wsl2 -e '(@ (gnu system images wsl2) wsl-os)'

Initially, when I wanted Guix on WSL, I thought it would be a huge pain. I was already using using the NixOS on WSL, and I had read skimmed through some articles explaining WSL image format, and my guess was I’d have to do lots of busy work to get a usable tarball1

I looked it up to see if anyone had done this before, and I came across two articles:

  1. This System Crafters article
  2. This GitHub gist

While the GH gist was a bit older (at least it’s calling it Guix System not GuixSD2), it still seemed like it was too much work.

Out of curiosity, I went ahead and searched in the Guix Info manual in Emacs (C-s wsl C-s) and learned that some fine folks have already done the work. If you don’t have Emacs, you can just search in the online manual. In fact, if you do guix system image --list-image-types, you’ll see WSL2 as one of the image types.

I did a bit of digging, and found wsl2.scm. Not only does Guix provide a wsl2 image builder, there’s also this sample wsl-os system object that you can use.

Now, the command above should make sense, and you should be able to build your own image.

Importing

Now, one way to import the image you just built is to somehow send it to your Windows machine and import it like this in powershell:

wsl --import guix $HOME\Guix .\guix-wsl.tar.gz

But if you have SSH access, it’s much simpler. Remember that Guix (unlike Nix that leaves residue ./result symlinks in the working directory) returns the path of the built file as the output. Using this simple fact, you can have a one-liner to build, send, and import the image:

cat $(guix system image --expression='(@ (gnu system images wsl2) wsl-os)' --image-type=wsl2) | ssh windows-machine wsl --import guix C:\Guix -
  • To explain this, the $(...) portion builds and outputs the path of the built tarball
  • cat prints out the content of the tarball to the standard output.
  • |ssh windows-machine ... is the fun part where the remote Windows machine reads it into powershell’s standard input.
  • wsl --import guix C:\Guix - imports and creates the WSL distro under C:\Guix, calls it guix, and reads from standard input because of - (which I discovered thanks to wsl --help)

Pre-built images

I’d highly doubt there would ever be official pre-built images for public consumption; it just doesn’t make sense considering GNU’s goals. Because of that, I set up this repo and GitHub workflow thanks to a GitHub action I found for guix. It builds and adds the stock wsl guix image to the release that you can easily import.

It’s very barebones with no instructions, but it’s a good starting point so that folks who don’t have a Linux machine or don’t want to go through the trouble of setting up Guix could easily download the release and use it on Windows.

Resources for the curious

Microsoft’s guide on how to build WSL distros
https://learn.microsoft.com/en-us/windows/wsl/build-custom-distro
Building a WSL tarball from a Docker image
https://learn.microsoft.com/en-us/windows/wsl/use-custom-distro
How NixOS builds its WSL tarball
https://github.com/nix-community/NixOS-WSL/tree/main/modules
Suse’s wiki page on WSL
https://en.opensuse.org/openSUSE:WSL

  1. WSL images are simply tarballs like docker images, despite sometimes having .wsl extensions (just like .ova files). ↩︎

  2. Guix System used to be called GuixSD. ↩︎