Document bare metal installation via Calamares

hosts/moonarch holds machine independent settings only; the disk layout
comes from Calamares, which also produces hardware-configuration.nix.

DECISIONS.md

@@ -77,3 +77,18 @@
   output.
 - **How**: `virtio-vga-gl` with `gl=on`, and the VM is shut down when not in
   use. The underlying amdgpu problem is a host issue, unrelated to Moonarch.
+
+## 2026-08-07 – Disk layout via Calamares, not disko
+
+- **Who**: Dominik
+- **Why**: Stage 3 targets bare metal, but no target machine exists yet —
+  neither the number of disks nor their device paths are known.
+- **Tradeoffs**: `disko` would put partitioning and encryption under version
+  control, which pays off when reinstalling often or setting up several
+  machines alike. For a single machine it is extra work without return, and it
+  would require guessing device paths. Calamares already covers partitioning,
+  LUKS and hardware detection, and produces `hardware-configuration.nix` — the
+  one file that cannot be written in advance.
+- **How**: `hosts/moonarch/` holds only machine independent settings.
+  Installation runs through Calamares, then the generated hardware file is
+  copied into the host directory. See README.md.

README.md

@@ -45,6 +45,55 @@ Activate:
 sudo nixos-rebuild switch --flake .#moonarch-vm
 ```
 
+## Installing on bare metal
+
+The disk layout is not declared here. Calamares handles partitioning,
+encryption and hardware detection, and produces the one file that cannot be
+written in advance: `hardware-configuration.nix` with the machine's UUIDs,
+LUKS devices and kernel modules.
+
+1. Boot the NixOS ISO and run Calamares. Choose `dkressler` as the user name —
+   that is what `hosts/moonarch/default.nix` declares. Pick btrfs, snapper
+   expects it.
+2. Reboot into the fresh system. It runs on the configuration Calamares
+   generated, without Moonarch.
+3. Enable flakes and install git — neither is available yet:
+
+   ```bash
+   sudo nano /etc/nixos/configuration.nix
+   #   nix.settings.experimental-features = [ "nix-command" "flakes" ];
+   #   environment.systemPackages = with pkgs; [ git ];
+   sudo nixos-rebuild switch
+   ```
+
+4. Clone this repo and take over the hardware file:
+
+   ```bash
+   git clone https://gitea.moonarch.de/nevaforget/moonix.git
+   cp /etc/nixos/hardware-configuration.nix moonix/hosts/moonarch/
+   ```
+
+5. Add the import to `hosts/moonarch/default.nix`:
+
+   ```nix
+   imports = [ ./hardware-configuration.nix ];
+   ```
+
+6. Switch and reboot:
+
+   ```bash
+   sudo nixos-rebuild switch --flake ~/moonix#moonarch
+   ```
+
+If step 6 breaks the system, pick the previous generation in the boot menu —
+the Calamares install stays available as generation 1.
+
+Still missing afterwards: a `nixos-hardware` profile for the specific model
+(firmware, power management, model quirks). It can be added at any time.
+
+`nixosConfigurations.moonarch` therefore evaluates but is not installable on
+its own: without `hardware-configuration.nix` it has no filesystems.
+
 ## Version bumps
 
 The project repos are pinned to release tags. After tagging a new version:

flake.nix

@@ -7,6 +7,7 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
 
+
     # Project sources. These repos are not flakes themselves, they are
     # consumed as plain source trees pinned to a release tag.
     moonarch = {
@@ -87,12 +88,26 @@
         };
       };
 
-      nixosConfigurations.moonarch-vm = nixpkgs.lib.nixosSystem {
-        inherit system;
-        modules = [
-          ./hosts/moonarch-vm
-          self.nixosModules.moonarch
-        ];
+      nixosConfigurations = {
+        # QEMU test VM.
+        moonarch-vm = nixpkgs.lib.nixosSystem {
+          inherit system;
+          modules = [
+            ./hosts/moonarch-vm
+            self.nixosModules.moonarch
+          ];
+        };
+
+        # Bare metal. Machine independent settings only — no disk layout and
+        # no hardware profile, both depend on a target machine that is not
+        # decided yet. Not installable as is.
+        moonarch = nixpkgs.lib.nixosSystem {
+          inherit system;
+          modules = [
+            ./hosts/moonarch
+            self.nixosModules.moonarch
+          ];
+        };
       };
 
       devShells.${system}.default = pkgs.mkShell {

hosts/moonarch/default.nix

@@ -0,0 +1,67 @@
+# ABOUTME: Host configuration for the bare metal machine.
+# ABOUTME: Machine independent settings only — no disk layout, no hardware profile.
+
+{ pkgs, ... }:
+
+{
+
+  boot.loader.systemd-boot.enable = true;
+  boot.loader.efi.canTouchEfiVariables = true;
+  boot.kernelPackages = pkgs.linuxPackages_zen;
+  boot.kernelParams = [ "quiet" ];
+
+  networking.hostName = "moonarch";
+  networking.networkmanager.enable = true;
+
+  time.timeZone = "Europe/Berlin";
+  i18n.defaultLocale = "de_DE.UTF-8";
+  i18n.extraLocaleSettings = {
+    LC_ADDRESS = "de_DE.UTF-8";
+    LC_IDENTIFICATION = "de_DE.UTF-8";
+    LC_MEASUREMENT = "de_DE.UTF-8";
+    LC_MONETARY = "de_DE.UTF-8";
+    LC_NAME = "de_DE.UTF-8";
+    LC_NUMERIC = "de_DE.UTF-8";
+    LC_PAPER = "de_DE.UTF-8";
+    LC_TELEPHONE = "de_DE.UTF-8";
+    LC_TIME = "de_DE.UTF-8";
+  };
+  console.keyMap = "de";
+  services.xserver.xkb.layout = "de";
+
+  users.users.dkressler = {
+    isNormalUser = true;
+    description = "Dominik Kressler";
+    extraGroups = [ "networkmanager" "wheel" "video" "input" "plugdev" "docker" ];
+    shell = pkgs.zsh;
+  };
+
+  # Snapshots of root and home. snap-pac has no counterpart here: NixOS keeps
+  # its own generations, so pre/post package snapshots are redundant.
+  services.snapper = {
+    configs = {
+      root = {
+        SUBVOLUME = "/";
+        ALLOW_USERS = [ "dkressler" ];
+        TIMELINE_CREATE = true;
+        TIMELINE_CLEANUP = true;
+      };
+      home = {
+        SUBVOLUME = "/home";
+        ALLOW_USERS = [ "dkressler" ];
+        TIMELINE_CREATE = true;
+        TIMELINE_CLEANUP = true;
+      };
+    };
+    snapshotInterval = "hourly";
+    cleanupInterval = "1d";
+  };
+
+  services.fstrim.enable = true;
+  services.fwupd.enable = true;
+
+  nix.settings.experimental-features = [ "nix-command" "flakes" ];
+  nixpkgs.config.allowUnfree = true;
+
+  system.stateVersion = "26.05";
+}