proof of concept

flake.lock

@@ -0,0 +1,43 @@
+{
+  "nodes": {
+    "nixos-hardware": {
+      "locked": {
+        "lastModified": 1632990363,
+        "narHash": "sha256-SNqz+9Vt4yDHqw8u/CMFdzMQTulKoMlVGJdshfcb5O0=",
+        "owner": "nixos",
+        "repo": "nixos-hardware",
+        "rev": "0a8b8054c9920368a3c15e6d766188fdf04b736f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "repo": "nixos-hardware",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1633550479,
+        "narHash": "sha256-LG9m2A3UMsFGEaY4XL2xqD7gGVTeeYiskjBbubCV9/4=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "b8f6eb7300e60a9c3b505ec381d0eab9029203e8",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "release-21.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixos-hardware": "nixos-hardware",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,46 @@
+{
+  description = "Image builder for RaspberryPi";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/release-21.05";
+    nixos-hardware.url = "github:nixos/nixos-hardware";
+  };
+
+  outputs = { self, nixpkgs, nixos-hardware }: {
+
+    nixosModules = {
+      defaults = import ./modules/defaults.nix;
+      pi = import ./modules/pi.nix;
+      pi4 = import ./modules/pi4.nix;
+      minetest = import ./modules/minetest.nix;
+    };
+
+    nixosConfigurations = {
+      pi4-minetest = nixpkgs.lib.nixosSystem {
+        system = "aarch64-linux";
+        modules = with self.nixosModules; [
+          "${nixpkgs}/nixos/modules/installer/sd-card/sd-image-aarch64.nix"
+          nixos-hardware.nixosModules.raspberry-pi-4
+          defaults pi pi4 minetest
+        ];
+      };
+    };
+
+    packages =
+      let
+        systems =
+          map (nixos:
+            nixos.config.system.build.toplevel.system
+          ) (builtins.attrValues self.nixosConfigurations);
+      in builtins.foldl' (result: system: result // {
+        "${system}" = nixpkgs.lib.mapAttrs (_: nixos:
+          nixos.config.system.build.sdImage
+        ) (
+          nixpkgs.lib.filterAttrs (_: nixos:
+            nixos.config.system.build.toplevel.system == system
+          ) self.nixosConfigurations
+        );
+      }) {} systems;
+
+  };
+}

modules/defaults.nix

@@ -0,0 +1,56 @@
+{ pkgs, ... }:
+{
+  nix = {
+    buildCores = 4;
+    maxJobs = 2;
+  };
+  networking = {
+    useDHCP = false;
+    interfaces.eth0.useDHCP = true;
+    firewall.enable = false;
+  };
+
+  security.sudo = {
+    enable = true;
+    wheelNeedsPassword = false;
+  };
+
+  users.users.pi = {
+    isNormalUser = true;
+    extraGroups = [ "wheel" "audio" "video" ];
+    initialPassword = "";
+  };
+
+  # Select internationalisation properties.
+  console = {
+    font = "${pkgs.terminus_font}/share/consolefonts/ter-u28n.psf.gz";
+    keyMap = "de";
+  };
+
+  # Enable the X11 windowing system.
+  services.xserver.enable = true;
+  services.xserver.layout = "de";
+  services.xserver.xkbOptions = "eurosign:e";
+
+  services.xserver.displayManager = {
+    lightdm = { enable = true; };
+    autoLogin = {
+      enable = true;
+      user = "pi";
+    };
+  };
+  services.xserver.desktopManager = {
+    xfce.enable = true;
+  };
+
+  documentation = {
+    enable = false;
+    dev.enable = false;
+    doc.enable = false;
+    info.enable = false;
+    man.enable = false;
+    nixos.enable = false;
+  };
+
+  system.stateVersion = "21.05";
+}

modules/minetest.nix

@@ -0,0 +1,20 @@
+{ pkgs, ... }:
+{
+  networking.hostName = "minetest";
+
+  environment.systemPackages = with pkgs; [
+    minetest
+  ];
+
+  nixpkgs.config.packageOverrides = pkgs: {
+    irrlicht = pkgs.irrlicht.overrideAttrs (oa: {
+      CPPFLAGS="-DPNG_ARM_NEON_OPT=0";
+      buildPhase = ''
+        make -j$NIX_BUILD_CORES sharedlib NDEBUG=1 "LDFLAGS=-lX11 -lGL -lXxf86vm"
+      '';
+    });
+    minetest = pkgs.minetest.overrideAttrs (oa: {
+      enableParallelBuilding = true;
+    });
+  };
+}

modules/pi.nix

@@ -0,0 +1,50 @@
+{ pkgs, config, lib, ... }:
+{
+  sdImage = {
+    compressImage = false;
+    imageBaseName = config.networking.hostName;
+    firmwareSize = 64;
+  };
+
+  boot = {
+    loader = {
+      grub.enable = false;
+      generic-extlinux-compatible.enable = lib.mkDefault true;
+      raspberryPi = {
+        enable = true;
+        uboot.enable = true;
+        firmwareConfig = ''
+          gpu_mem=192
+          dtparam=audio=on
+        '';
+      };
+    };
+    kernelPackages = pkgs."linuxPackages_rpi${toString config.boot.loader.raspberryPi.version}";
+    kernelParams = [
+      "snd_bcm2835.enable_headphones=1"
+    ];
+    # Don't build ZFS for aarch64 (broken?)
+    supportedFilesystems = lib.mkForce [ "vfat" "ext4" ];
+    # Work around missing sun4i-drm.ko
+    initrd.availableKernelModules = lib.mkForce [ "vc4" ];
+
+    tmpOnTmpfs = true;
+  };
+  hardware.deviceTree = {
+    enable = true;
+    kernelPackage = config.boot.kernelPackages.kernel;
+  };
+
+  hardware.enableRedistributableFirmware = true;
+  powerManagement.cpuFreqGovernor = lib.mkDefault "performance";
+
+  environment.systemPackages = with pkgs; [
+    libraspberrypi
+    raspberrypi-eeprom
+  ];
+
+  # Do not log to sdcard:
+  services.journald.extraConfig = ''
+    Storage=volatile
+  '';
+}

modules/pi4.nix

@@ -0,0 +1,7 @@
+{ pkgs, ... }:
+{
+  boot.loader.raspberryPi.version = 4;
+  hardware.raspberry-pi."4" = {
+    fkms-3d.enable = true;
+  };
+}