Restructure flake.nix for a simpler config for building different images off the same NixOS config.

nix/configuration/formats/iso.nix

@@ -0,0 +1,23 @@
+{
+  lib,
+  modulesPath,
+  ...
+}:
+
+{
+  imports = [
+    (modulesPath + "/installer/cd-dvd/iso-image.nix")
+  ];
+
+  config = {
+    isoImage.makeEfiBootable = true;
+    isoImage.makeUsbBootable = true;
+
+    me.buildingPortable = true;
+    me.mountPersistence = lib.mkForce false;
+    me.optimizations.enable = lib.mkForce false;
+    me.image_based_appliance.enable = true;
+
+    # TODO: image based appliance?
+  };
+}

nix/configuration/formats/sd.nix

@@ -0,0 +1,32 @@
+{
+  modulesPath,
+  ...
+}:
+
+{
+  imports = [
+    (modulesPath + "/installer/sd-card/sd-image.nix")
+  ];
+
+  config = {
+    isoImage.makeEfiBootable = true;
+    isoImage.makeUsbBootable = true;
+
+    boot.loader.grub.enable = false;
+    boot.loader.generic-extlinux-compatible.enable = true;
+
+    # TODO: image based appliance?
+
+    # TODO: Maybe this?
+    # fileSystems = {
+    #   "/" = {
+    #     device = "/dev/disk/by-label/NIXOS_SD";
+    #     fsType = "ext4";
+    #     options = [
+    #       "noatime"
+    #       "norelatime"
+    #     ];
+    #   };
+    # };
+  };
+}

nix/configuration/formats/toplevel.nix

@@ -0,0 +1 @@
+{ }

nix/configuration/formats/vm_iso.nix

@@ -0,0 +1,21 @@
+{
+  modulesPath,
+  ...
+}:
+
+{
+  imports = [
+    (modulesPath + "/installer/cd-dvd/iso-image.nix")
+    (modulesPath + "/profiles/qemu-guest.nix") # VirtIO kernel modules
+  ];
+
+  config = {
+    isoImage.makeEfiBootable = true;
+    isoImage.makeUsbBootable = true;
+
+    networking.dhcpcd.enable = true;
+    networking.useDHCP = true;
+
+    me.image_based_appliance.enable = true;
+  };
+}