using nixos-anywhere

hosts/buildbox/configuration.nix

@@ -17,9 +17,10 @@
     inputs.home-manager.nixosModules.default
   ];
 
-  # Bootloader.
+  # Bootloader. SeaBIOS/BIOS boot via GRUB installed to the whole disk
+  # (writes boot.img to the MBR, core.img to the EF02 partition).
   boot.loader.grub.enable = lib.mkDefault true;
-  boot.loader.grub.devices = ["nodev"];
+  boot.loader.grub.devices = ["/dev/sda"];
 
   nix.settings.experimental-features = ["nix-command" "flakes"];
 

hosts/buildbox/disko-config.nix

@@ -13,6 +13,17 @@
         content = {
           type = "gpt";
           partitions = {
+            # GRUB's core.img lives here on GPT/BIOS systems (GPT leaves no
+            # gap after the MBR, so grub-install needs an EF02 partition).
+            # Not mounted; grub-install writes the boot code directly.
+            boot = {
+              size = "1M";
+              type = "EF02";
+              content = {
+                type = "filesystem";
+                format = "empty";
+              };
+            };
             root = {
               size = "100%";
               content = {

hosts/buildbox/hardware-configuration.nix

@@ -1,6 +1,15 @@
-# Do not modify this file!  It was generated by 'nixos-generate-config'
-# and may be overwritten by future invocations.  Please make changes
-# to /etc/nixos/configuration.nix instead.
+# Hardware profile for buildbox (QEMU/KVM VM).
+#
+# Filesystems, swap, and boot-related disk config are intentionally NOT
+# declared here — they are owned by disko via ./disko-config.nix, which
+# sets config.fileSystems / config.swapDevices / config.boot when
+# disko.enableConfig = true (the default). Keep this file limited to
+# kernel modules and platform settings that disko does not manage.
+#
+# This file is still regenerated by `nixos-anywhere --generate-hardware-config
+# nixos-generate-config ./hosts/buildbox/hardware-configuration.nix`, so any
+# hand-edits here may be overwritten on the next install. The disko-owned
+# filesystem entries below are stripped on purpose; do not re-add them.
 {
   config,
   lib,
@@ -17,47 +26,7 @@
   boot.kernelModules = [];
   boot.extraModulePackages = [];
 
-  fileSystems."/" = {
-    device = "/dev/disk/by-partuuid/REPLACE-ME";
-    fsType = "btrfs";
-    options = ["subvol=root" "compress=zstd" "noatime"];
-  };
-
-  fileSystems."/home" = {
-    device = "/dev/disk/by-partuuid/REPLACE-ME";
-    fsType = "btrfs";
-    options = ["subvol=home" "compress=zstd" "noatime"];
-  };
-
-  fileSystems."/nix" = {
-    device = "/dev/disk/by-partuuid/REPLACE-ME";
-    fsType = "btrfs";
-    options = ["subvol=nix" "compress=zstd" "noatime"];
-  };
-
-  fileSystems."/var/log" = {
-    device = "/dev/disk/by-partuuid/REPLACE-ME";
-    fsType = "btrfs";
-    options = ["subvol=var-log" "compress=zstd" "noatime"];
-    neededForBoot = false;
-  };
-
-  fileSystems."/.snapshots" = {
-    device = "/dev/disk/by-partuuid/REPLACE-ME";
-    fsType = "btrfs";
-    options = ["subvol=snapshots" "compress=zstd" "noatime"];
-    neededForBoot = false;
-  };
-
-  swapDevices = [
-    {
-      device = "/var/lib/swapfile";
-      size = 4 * 1024;
-    }
-  ];
-
   networking.useDHCP = lib.mkDefault true;
-  # networking.interfaces.wlp0s20f3.useDHCP = lib.mkDefault true;
 
   nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
   hardware.cpu.intel.updateMicrocode = lib.mkDefault config.hardware.enableRedistributableFirmware;