refactor: make nanuqsaurus module-based; keep btrfs install profile

docs/adopt.md

@@ -0,0 +1,64 @@
+# Adopt Nanuqsaurus on an existing NixOS install (no repartitioning)
+
+This repo intentionally does **not** ship a “one size fits all” `nixosConfiguration` for installed systems.
+Disk layouts, filesystems, initrd modules, and bootloader details are machine-specific and live in your
+local `hardware-configuration.nix`.
+
+The recommended workflow is to create a **small local wrapper flake** that:
+
+- keeps your machine’s `hardware-configuration.nix` as the source of truth for mounts/boot,
+- imports `nanuqsaurus` as a feature/profile module from its URL,
+- keeps your personal changes in your own repo (or `/etc/nixos`).
+
+## 1) Create a wrapper flake in `/etc/nixos`
+
+On the target machine:
+
+1. Ensure you have a `hardware-configuration.nix` (generated by `nixos-generate-config`).
+2. Create `/etc/nixos/flake.nix` like this (adjust `hostName` and `stateVersion`):
+
+```nix
+{
+  description = "Local wrapper for the nanuqsaurus profile";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.11";
+    nanuqsaurus.url = "git+https://codeberg.org/randogoth/nanuqsaurus.git";
+    nanuqsaurus.inputs.nixpkgs.follows = "nixpkgs";
+  };
+
+  outputs =
+    { self, nixpkgs, nanuqsaurus, ... }:
+    {
+      nixosConfigurations.my-host = nixpkgs.lib.nixosSystem {
+        system = "x86_64-linux";
+        modules = [
+          ./hardware-configuration.nix
+          nanuqsaurus.nixosModules.nanuqsaurus
+
+          # Your local overrides/customizations:
+          ({ ... }: {
+            # Optional: change the default admin username ("admin")
+            nanuqsaurus.admin.username = "admin";
+            networking.hostName = "my-host";
+            system.stateVersion = "25.11";
+          })
+        ];
+      };
+    };
+}
+```
+
+## 2) Switch to it
+
+```bash
+sudo nixos-rebuild switch --flake /etc/nixos#my-host
+```
+
+## Updating later
+
+- If you keep `nanuqsaurus.url` pointing at the repo, you can update with:
+  - `nix flake update` (in `/etc/nixos`), then
+  - `sudo nixos-rebuild switch --flake /etc/nixos#my-host`
+
+- Keep all your machine-specific changes in the wrapper flake (additional modules, packages, services, etc.).

docs/install-help.txt

@@ -13,20 +13,28 @@ Pick a stable disk path (prefer /dev/disk/by-id/*) and run:
     --disk main /dev/disk/by-id/<your-disk> \
     --mount-point /mnt
 
+Adopt an existing NixOS install (no repartition)
+-----------------------------------------------
+
+Create a small local wrapper flake that imports this repo as a module and keeps
+your machine’s `hardware-configuration.nix` for mounts/boot.
+
+See: docs/adopt.md (on the custom ISO: `/etc/nixos/docs/adopt.md`)
+
 
 ISO shortcut
 ------------
 
 If you are using the custom ISO from this repo, it embeds the flake at /etc/nixos.
-You can run the wrapper script (defaults: DISK=/dev/vda, TARGET_HOST=nanuqsaurus):
+You can run the wrapper script (defaults: DISK=/dev/vda, TARGET_HOST=nanuqsaurus-btrfs):
 
   sudo /etc/nixos/scripts/install-btrfs.sh
 
 
 Optionally set DISK, TARGET_HOST, and FLAKE:
 
-  sudo DISK=/dev/disk/by-id/<your-disk> TARGET_HOST=nanuqsaurus \
-    FLAKE="github:<owner>/<repo>" \
+  sudo DISK=/dev/disk/by-id/<your-disk> TARGET_HOST=nanuqsaurus-btrfs \
+    FLAKE="git+https://codeberg.org/<owner>/<repo>.git" \
     /etc/nixos/scripts/install-btrfs.sh