nixos/uki: the uki module depnds on the toplevel derivation

[programmerlexi]

Nixpkgs version

• Unstable (26.05)

Describe the bug

As of now the uki module depends on the toplevel derivation, making usage of the module from within the config impossible.

Steps to reproduce

Try using the uki module in the config (for example #413434)

Expected behaviour

uki module is usable

Screenshots

No response

Relevant log output

Additional context

No response

System metadata

• system: "x86_64-linux"
• host os: Linux 6.18.0-cachyos, NixOS, 26.05 (Yarara), 26.05.20251208.addf7cf
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.31.2+1
• nixpkgs: /nix/store/98mad1s6hrryyflb6qf6hd4xyb8r7cy4-source

Notify maintainers

@nikstur

---

Note for maintainers: Please tag this issue in your pull request description. (i.e. Resolves #ISSUE.)

I assert that this issue is relevant for Nixpkgs

• I assert that this is a bug and not a support request.
• I assert that this is not a duplicate of an existing issue.
• I assert that I have read the NixOS Code of Conduct and agree to abide by it.

Is this issue important to you?

Add a 👍 reaction to issues you find important.

[nikstur]

This is by design. This module only serves to create UKIs to be used in image builds.

To use a UKI in the normal NixOS way, the bootloader installer needs to generate it "out of band" (i.e. outside the toplevel derivation).

A UKI cannot be part of the toplevel derivation because it contains the kernel commandline which in turn references the toplevel. Thus creating an infinite recursion.