imageBuilder: add btrfs support

[lheckemann]

This is just a draft, I'm still waiting for my image build to complete so I can test it, and the btrfs builder looks a little different from the others — mostly because I don't understand the purpose of the scope stuff in the others;

With a local.nix containing

  mobile.generatedFilesystems.rootfs = lib.mkDefault {
    type = lib.mkForce "btrfs";
    id = lib.mkForce "b8ec3817-2e82-4c93-9870-6d502fdcb423";
  };
  fileSystems."/" = {
    fsType = "btrfs";
    device = "/dev/disk/by-uuid/b8ec3817-2e82-4c93-9870-6d502fdcb423";
  };

this built and booted successfully \o/

[samueldr]

You won't (or will) believe me, but the main reason I hadn't taken a look at this yet is because I needed to explain the scope thingy, which I really vaguely knew the reason, but didn't want to handwave it as "oh, it's to name the functions".

So, here goes:

• https://github.com/samueldr/nix-named-scopes-trick

This is why I'm doing that weird trick. It makes wrong use somewhat more user-friendly... Though not all wrong uses end up being made more user friendly :/

[samueldr]

Other than the "scope" stuff, it looks alright.

Can you add he scope stuff, also spacing with an empty line like the following:

• mobile-nixos/lib/image-builder/makeFAT32.nix

  Lines 2 to 4 in a0f9ae0

  	/* */ let scope = { "fileSystem.makeFAT32" =

• mobile-nixos/lib/image-builder/makeFAT32.nix

  Lines 106 to 107 in a0f9ae0

  	/* */ ;}; in scope."fileSystem.makeFAT32"

If you want me to take care of it, just ask :).

[lheckemann]

Done! Any particular reason to use let scope = { "…" = as opposed to let scope."…" =?

[samueldr]

Thanks!

None really, I guess I didn't think about how that would work when I implemented it.

[kurnevsky]

It doesn't work anymore, I got errors like:

modprobe: module btrfs not found in modules.dep
W, [2023-03-07T12:58:01.179669//1.6682 #1]  WARN -- : Kernel filesystem module “btrfs” failed to load.
mount: mounting /dev/disk/by-uuid/e3b552a3-be28-4d1d-9016-e1b9a8699464 on /mnt/ failed: No such device

[samueldr]

That may not be that the image generated didn't work, but that the device you are attempting to boot on doesn't have the BTRFS driver enabled.

Since you're now booting to a system, I would highly suspect that the image building worked.

Can you open a new issue (since this is unrelated to this PR), explaining what you are attempting to do (I suspect something like building a device image with BTRFS), what you have tried, and what you are observing? Don't forget to include useful information like the device you're building for, and exact commands used.

Thank you.