Fix stinky build.

hosts/stinky/hardware.nix

@@ -13,25 +13,45 @@
   # Raspberry Pi 4 platform
   nixpkgs.hostPlatform = lib.mkDefault "aarch64-linux";
 
+  # Disable ZFS (not needed, and broken with latest kernel)
+  boot.supportedFilesystems.zfs = lib.mkForce false;
+
   # Boot configuration - provided by sd-image-aarch64.nix
   # (grub disabled, generic-extlinux-compatible enabled, U-Boot setup)
 
-  # Override root filesystem to use tmpfs (from impermanence-tmpfs.nix)
-  # The sd-image module sets root to /dev/disk/by-label/NIXOS_SD (ext4)
-  # but impermanence-tmpfs.nix overrides it to tmpfs
-
   # /boot/firmware is automatically configured by sd-image module
   # Device: /dev/disk/by-label/FIRMWARE (vfat)
 
-  # Mount /nix from the NIXOS_SD partition
-  # /nix/persist will be a directory on this partition (not a separate mount)
-  fileSystems."/nix" = {
+  # tmpfs root with impermanence
+  # Override sd-image module's ext4 root definition with mkForce
+  fileSystems."/" = lib.mkForce {
+    device = "none";
+    fsType = "tmpfs";
+    options = [
+      "defaults"
+      "size=2G"
+      "mode=755"
+    ];
+  };
+
+  # The SD partition contains /nix/store and /nix/persist at its root
+  # Mount it at a hidden location, then bind mount its /nix to /nix
+  fileSystems."/mnt/nixos-sd" = {
     device = "/dev/disk/by-label/NIXOS_SD";
     fsType = "ext4";
     options = [ "noatime" ];
     neededForBoot = true;
   };
 
+  # Bind mount /nix from the SD partition
+  fileSystems."/nix" = {
+    device = "/mnt/nixos-sd/nix";
+    fsType = "none";
+    options = [ "bind" ];
+    neededForBoot = true;
+    depends = [ "/mnt/nixos-sd" ];
+  };
+
   # No swap on SD card (wear concern)
   swapDevices = [ ];