Failed to build SD image for armv6l-linux (RPi Pico W) due to bootstrap-tools

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1

I’m trying to build an SD image of NixOS for my Raspberry Pi Pico W. The machine’s architecture is armv6l-linux and my approach is to cross-compile from x86_64-linux. Here’s my flake from NixOS on ARM - NixOS Wiki

{
  description = "Build image";
  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
  outputs = { self, nixpkgs }: let 
    system = "armv6l-linux";
    pkgs = nixpkgs.legacyPackages.${system};
  in rec {
    nixosConfigurations.rpizw = nixpkgs.lib.nixosSystem {
      modules = [
        "${nixpkgs}/nixos/modules/installer/sd-card/sd-image-raspberrypi.nix"
        {
          nixpkgs.config.allowUnsupportedSystem = true;
          nixpkgs.hostPlatform.system = system;
          nixpkgs.buildPlatform.system = "x86_64-linux"; #If you build on x86 other wise changes this.
          nixpkgs.overlays = [
            (self: super: {
              # https://github.com/rhboot/efivar/issues/270
              # I don't need efivar, I think.
              efivar = pkgs.runCommand "empty-efivar" { } "mkdir -p $out";
              efibootmgr = pkgs.runCommand "empty-efibootmgr" { } "mkdir -p $out";
            })
          ];
        }
      ];
    };
    images.rpizw = nixosConfigurations.rpizw.config.system.build.sdImage;
  };
}

The build (nix build .#images.rpizw) cannot get pass bootstrap-tools:

error: '/nix/store/n3ds4hlxnbp6fwc0l90f4ygakakcchlw-bootstrap-tools.drv': build not possible: unknown system: armv6l-linux

I tried with pinning nixpkgs to nixos-24.11 but I get the same error.

What’s the problem here, and is there a way to solve this? Thanks in advance!

2

pkgs is provided as part of the NixOS module system.

{
  description = "Build image";
  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
  outputs = { self, nixpkgs }: let 
    system = "armv6l-linux";
    pkgs = nixpkgs.legacyPackages.${system};
  in rec {
    nixosConfigurations.rpizw = nixpkgs.lib.nixosSystem {
      modules = [
        "${nixpkgs}/nixos/modules/installer/sd-card/sd-image-raspberrypi.nix"
        ({pkgs, ...}: {
          nixpkgs.config.allowUnsupportedSystem = true;
          nixpkgs.hostPlatform.system = system;
          nixpkgs.buildPlatform.system = "x86_64-linux"; #If you build on x86 other wise changes this.
          nixpkgs.overlays = [
            (self: super: {
              # https://github.com/rhboot/efivar/issues/270
              # I don't need efivar, I think.
              efivar = pkgs.runCommand "empty-efivar" { } "mkdir -p $out";
              efibootmgr = pkgs.runCommand "empty-efibootmgr" { } "mkdir -p $out";
            })
          ];
        })
      ];
    };
    images.rpizw = nixosConfigurations.rpizw.config.system.build.sdImage;
  };
}
3

Ohh thank you! This gets me past this error.