nixos/systemd-boot: Add support for an XBOOTLDR partition

[sdht0]

Description of changes

Continuation of PR #260241 which I closed inadvertently.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[sdht0]

@nikstur @RaitoBezarius ideally qemu-vm should provide an option to override the systemImage. However, I avoided making any changes and indirectly used useBootLoader=false option as a workaround.

[sdht0]

@nikstur @RaitoBezarius gentle ping

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/how-to-put-my-kernels-initrd-and-entries-in-the-boot-xbootldr-partition/19162/4

[sdht0]

@nikstur @RaitoBezarius can you please take a look at the last blocker for this PR? Specifically these lines.

[nikstur]

Looks good from my side.

[sdht0]

Thanks.

@ElvishJerricco @JulienMalka can we merge this then?

cc @RaitoBezarius

[JulienMalka]

@ofborg test systemd-boot

[sdht0]

Fixed a merge conflict.

[sdht0]

@ofborg test systemd-boot

[ElvishJerricco]

LGTM. @RaitoBezarius shall we merge?

[RaitoBezarius]

Let's go, I want to say that @sdht0 you have been incredibly patient with us, I would like to point out this is something I rarely see in nixpkgs contributions and a big big big thank you, this has been a very pleasant experience for me to review, even beyond the disagreements.

[sdht0]

Thanks for the kind words @RaitoBezarius!

Nice to get this finally in. Thanks @JulienMalka @ElvishJerricco @nikstur for the reviews.

And thanks again @colemickens for handing over your PR. I got to have quite a bit of fun.

[colemickens]

Very cool that (the original accidentally closed) PR was your first PR in nixpkgs, @sdht0! Quite a cool first contribution, and more already since then. 😎 🚀

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/add-windows-to-boot-menu/40675/5