nixos-iot-node/workspace/rpi2.nix

{ config, pkgs, lib, ... }:

{
  imports = [ <nixpkgs/nixos/modules/installer/sd-card/sd-image.nix> ];

  # Define the image name
  sdImage.imageBaseName = "nixos-rpi2";
  sdImage.compressImage = false;

  # Required: Set populateRootCommands
  sdImage.populateRootCommands = ''
    mkdir -p ./files
    echo "NixOS for Raspberry Pi 2" > ./files/welcome.txt
  '';
  sdImage.populateFirmwareCommands = "";

  # Bootloader: Use U-Boot for Raspberry Pi 2
  boot.loader.generic-extlinux-compatible.enable = true;
  hardware.deviceTree.enable = true;
  hardware.deviceTree.name = "bcm2709-rpi-2-b.dtb"; # Correct DTB for RPi2

  # Disable GRUB (not used on Raspberry Pi)
  boot.loader.grub.enable = false;

  # Qemu storage drivers
  # boot.initrd.enable = true;
  # boot.initrd.kernelModules = [ "brcmfmac" "bcm2835_rng" "mmc_block" "sdhci" "sdhci-pci" "sdhci-pltfm" ];
  # boot.initrd.network.enable = false;
  # boot.initrd.availableKernelModules = [ "mmc_block" "sdhci" "usb_storage" "ext4" ];
  
  # boot.initrd.availableKernelModules = [ "virtio_blk" "virtio_pci" "virtio_mmio" ];
  # boot.kernelModules = [ "virtio_blk" "virtio_net" "sd" "sdhci" ];
  # hardware.enableAllFirmware = true;
  boot.kernelPackages = lib.mkForce pkgs.linuxPackages_rpi2;
  nixpkgs.overlays = [
    (final: super: {
      makeModulesClosure = x:
        super.makeModulesClosure (x // { allowMissing = true; });
    })
  ];
  boot.supportedFilesystems = lib.mkForce [ "vfat" "ext4" ];
  
  # Networking
  networking.hostName = "nixos-rpi2";
  networking.wireless.enable = false; # Enable this if using WiFi
  networking.interfaces.eth0.useDHCP = true;

  # Enable SSH
  services.openssh.enable = true;

  # User setup
  users.users.nixos = {
    isNormalUser = true;
    initialPassword = "nixos";
    extraGroups = [ "wheel" ];
  };
  users.groups.nixos = {};
  
  # Set system version (avoid warnings)
  system.stateVersion = "25.05";
}