feat: Enable system flake additions from external files

README.md

@@ -92,6 +92,94 @@ hdh20267 = {
 
 The external flake must provide a `homeManagerModules.default` output. Note that using this feature may require running `update-system --impure` if the flake is not locked in the system's `flake.lock`.
 
+### Using External Flakes for System Configuration
+
+You can also override the system-level configuration for a specific host using an external flake. This is useful for adding system services (like Docker), changing boot parameters, or installing system-wide packages that are not in the standard image.
+
+1.  Open `inventory.nix`.
+2.  In the `devices` override for the host, set the `flakeUrl`:
+
+```nix
+nix-laptop = {
+  count = 2;
+  devices = {
+    "2" = { 
+      flakeUrl = "github:myuser/my-system-config"; 
+      # You can still combine this with other overrides
+      swapSize = "64G";
+    };
+  };
+};
+```
+
+The external flake must provide a `nixosModules.default` output.
+
+## External Flake Templates
+
+If you are creating a new flake to use with `flakeUrl`, use these templates as a starting point.
+
+### Home Manager Flake (for `users.nix`)
+
+Use this for user-specific dotfiles, shell configuration, and user packages.
+
+```nix
+{
+  description = "My Home Manager Configuration";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    # home-manager is not strictly required as an input if you only export a module,
+    # but it's good practice for standalone testing.
+  };
+
+  outputs = { self, nixpkgs, ... }: {
+    # This output is what nixos-systems looks for
+    homeManagerModules.default = { pkgs, ... }: {
+      home.stateVersion = "25.11";
+      
+      home.packages = with pkgs; [ 
+        ripgrep 
+        bat 
+        fzf
+      ];
+
+      programs.git = {
+        enable = true;
+        userName = "My Name";
+        userEmail = "me@example.com";
+      };
+    };
+  };
+}
+```
+
+### System Flake (for `inventory.nix`)
+
+Use this for host-specific system services, hardware tweaks, or root-level packages.
+
+```nix
+{
+  description = "My System Configuration Override";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-25.11";
+  };
+
+  outputs = { self, nixpkgs, ... }: {
+    # This output is what nixos-systems looks for
+    nixosModules.default = { pkgs, ... }: {
+      environment.systemPackages = [ pkgs.docker ];
+      
+      virtualisation.docker.enable = true;
+      
+      # Example: Add a custom binary cache
+      nix.settings.substituters = [ "https://nix-community.cachix.org" ];
+      nix.settings.trusted-public-keys = [ "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs=" ];
+    };
+  };
+}
+```
+
 ### Adding a New Host
 
 1.  Open `inventory.nix`.

hosts/default.nix

@@ -47,22 +47,36 @@ let
   mkHostGroup = { prefix, count, system ? "x86_64-linux", extraModules ? [], deviceOverrides ? {} }:
     lib.listToAttrs (map (i: {
       name = "${prefix}${toString i}";
-      value = mkHost {
-        hostName = "${prefix}${toString i}";
-        inherit system;
-        extraModules = extraModules ++ 
-          (lib.optional (builtins.hasAttr (toString i) deviceOverrides) 
-            ({ ... }: 
-              let
-                devConf = deviceOverrides.${toString i};
-                fsConf = builtins.removeAttrs devConf [ "extraUsers" ];
-              in {
-                host.filesystem = fsConf;
-                modules.users.enabledUsers = devConf.extraUsers or [];
-              }
-            )
-          );
-      };
+      value = 
+        let
+          devConf = deviceOverrides.${toString i} or {};
+          hasOverride = builtins.hasAttr (toString i) deviceOverrides;
+          
+          # Extract flakeUrl if it exists
+          externalFlake = if hasOverride && (builtins.hasAttr "flakeUrl" devConf) 
+                          then builtins.getFlake devConf.flakeUrl 
+                          else null;
+          
+          # Module from external flake
+          externalModule = if externalFlake != null 
+                           then externalFlake.nixosModules.default 
+                           else {};
+
+          # Config override module
+          overrideModule = { ... }: 
+            let
+              # Remove special keys that are not filesystem options
+              fsConf = builtins.removeAttrs devConf [ "extraUsers" "flakeUrl" ];
+            in lib.mkIf hasOverride {
+              host.filesystem = fsConf;
+              modules.users.enabledUsers = devConf.extraUsers or [];
+            };
+        in
+        mkHost {
+          hostName = "${prefix}${toString i}";
+          inherit system;
+          extraModules = extraModules ++ [ overrideModule ] ++ (lib.optional (externalFlake != null) externalModule);
+        };
     }) (lib.range 1 count));
 
   # Generate host groups based on the input hosts configuration

hosts/user-config.nix

@@ -3,7 +3,7 @@ let
   userSubmodule = lib.types.submodule {
     options = {
       isNormalUser = lib.mkOption { type = lib.types.bool; default = true; };
-      description = lib.mkOption { type = lib.types.nullOr lib.types.str; default = null; };
+      description = lib.mkOption { type = lib.types.str; default = ""; };
       extraGroups = lib.mkOption { type = lib.types.listOf lib.types.str; default = []; };
       hashedPassword = lib.mkOption { type = lib.types.str; default = "!"; };
       extraPackages = lib.mkOption { type = lib.types.listOf lib.types.package; default = []; };
@@ -49,9 +49,7 @@ in
         finalPackages = lib.subtractLists user.excludePackages (defaultPackages ++ user.extraPackages);
       in
       {
-        inherit (user) isNormalUser extraGroups hashedPassword;
-        description = if user.description != null then user.description else lib.mkDefault "";
-        openssh.authorizedKeys.keys = user.opensshKeys;
+        inherit (user) isNormalUser description extraGroups hashedPassword;
         packages = finalPackages;
         shell = config.modules.users.shell;
       }
@@ -68,7 +66,7 @@ in
           enabledAccounts = lib.filterAttrs (name: _: lib.elem name config.modules.users.enabledUsers) config.modules.users.accounts;
         in
         lib.mapAttrs (name: user: { ... }: {
-          imports = user.extraImports ++ 
+          imports = user.extraImports ++ [ ../sw/theme.nix ../sw/nvim.nix ] ++
             (lib.optional (user.flakeUrl != "") (builtins.getFlake user.flakeUrl).homeManagerModules.default);
           home.username = name;
           home.homeDirectory = if name == "root" then "/root" else "/home/${name}";

inventory.nix

@@ -10,18 +10,17 @@
       # Enable specific users for this device index
       "1" = { extraUsers = [ "hdh20267" ]; };
       "2" = { extraUsers = [ "hdh20267" ]; };
+      
+      # Example of using an external flake for system configuration:
+      # "2" = { flakeUrl = "github:user/system-flake"; };
     };
   };
 
   # Desktop Configuration
   # Base specs: NVMe drive, 16G Swap
-  nix-desktop = {
-    count = 1;
-  };
+  nix-desktop.count = 1;
 
   # Surface Tablet Configuration (Kiosk Mode)
   # Base specs: eMMC drive, 8G Swap
-  nix-surface = {
-    count = 3;
-  };
+  nix-surface.count = 3;
 }

users.nix

@@ -6,21 +6,17 @@
     root = {
       isNormalUser = false;
       hashedPassword = "!";
-      extraImports = [ ./sw/theme.nix ];
-      opensshKeys = [ "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIBC7xzHxY2BfFUybMvG4wHSF9oEAGzRiLTFEndLvWV/X hdh20267@engr733847d.engr.uga.edu" ];
     };
     engr-ugaif = {
       description = "UGA Innovation Factory";
       extraGroups = [ "networkmanager" "wheel" "video" "input" ];
       hashedPassword = "$6$El6e2NhPrhVFjbFU$imlGZqUiizWw5fMP/ib0CeboOcFhYjIVb8oR1V1dP2NjDeri3jMoUm4ZABOB2uAF8UEDjAGHhFuZxhtbHg647/";
-      extraImports = [ ./sw/theme.nix ./sw/nvim.nix ];
       opensshKeys = [ "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIBC7xzHxY2BfFUybMvG4wHSF9oEAGzRiLTFEndLvWV/X hdh20267@engr733847d.engr.uga.edu" ];
     };
     hdh20267 = {
       description = "Hunter Halloran";
       extraGroups = [ "networkmanager" "wheel" ];
       homePackages = [ pkgs.ghostty ];
-      extraImports = [ ./sw/theme.nix ./sw/nvim.nix ];
       # Example of using an external flake for configuration:
       # flakeUrl = "github:hdh20267/dotfiles";
     };