1. Change all UUID partition references to /dev/sda or /dev/sda2.

2. Made sure that btrfs was present during boot.

3. Expanded the boot device definition to have more details vs. the previous version which just had the path.

  # Disable UEFI.
  boot.loader.systemd-boot.enable = false;

  # Use the GRUB 2 boot loader.
  boot.loader.grub.enable = true;
  boot.loader.grub.efiSupport = false;
  boot.loader.grub.enableCryptodisk = true;

  boot.loader.efi.canTouchEfiVariables = false;
  # boot.loader.grub.efiInstallAsRemovable = true;
  # boot.loader.efi.efiSysMountPoint = "/boot/efi";
  # Define on which hard drive you want to install Grub.
  boot.loader.grub.device = "/dev/sda"; # or "nodev" for efi only

  
  boot.initrd.luks.devices.cryptroot.devices = [
    {
      name = "luksroot";
      device = "/dev/sda2";
    }
  ];

  boot.initrd.supportedFilesystems = [ "btrfs" ];

{
  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-24.11";
  inputs.disko.url = "github:nix-community/disko/latest";
  inputs.disko.inputs.nixpkgs.follows = "nixpkgs";

  outputs = {self, disko, nixpkgs }: {
    nixosConfigurations.koolthing = nixpkgs.legacyPackages.x86_64-linux.nixos [
      ./configuration.nix
      disko.nixosModules.disko
      {
        disko.devices = {
	  disk = {
          main = {
            type = "disk";
            device = "/dev/sda";
            content = {
              type = "gpt";
              partitions = {
                # Legacy BIOS, MBR-style partition table.
                boot = {
                  size = "1M";
                  type = "EF02"; # Grub MBR.
                };

                # The LUKS-encrypted root.
                luks = {
                  size = "300G";
                  content = {
                    type = "luks";
                    name = "crypted";

                    # Set up with an interactive password and not a keyfile.
                    settings = {
                      allowDiscards = true;
                    };

                    # The Btrfs filesystem.
                    content = {
                      type = "btrfs";
                      extraArgs = ["-f"]; # Overwrite any existing file system.
                      subvolumes = {
                        "/root" = {
                          mountpoint = "/";
                          mountOptions = [
                            "compress=zstd"
                            "noatime"
                          ];
                        };

                        # The home subvolume.
                        "/home" = {
                          mountpoint = "/home";                          
                          mountOptions = [
                            "compress=zstd"
                            "noatime"
                          ];
                        };

                        # The nix subvolume.
                        "/nix" = {
                          mountpoint = "/nix";                          
                          mountOptions = [
                            "compress=zstd"
                            "noatime"
                          ];
                        };
                      };
                    };
                  };
                };
              };
            };
          };
	};
        };
      }
    ];
  };
}