Add documentation for NixOS and Home Manager conventions

2026-06-06 03:26:19 -03:00
parent 380b428d9a
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+# Conventions
+
+## How the flake is wired
+
+`flake.nix` runs import-tree on `./modules` with a few extra filters: skip `/package/`, `/packages/`, and `dms/home-manager/` (callPackage noise + DMS HM colocation). Don't add a global `/home-manager/` filter — `modules/ssh/home-manager/` needs to load.
+
+Every scanned `.nix` should be a flake fragment:
+
+```nix
+{ self, inputs, ... }: {
+  flake.nixosModules.systemFoo = { config, lib, pkgs, ... }: { /* … */ };
+}
+```
+
+Don't define the same `flake.nixosModules.foo` in two files — merge order isn't something to bet on.
+
+**Outputs I actually use:** `nixosConfigurations.*`, `nixosModules.*`, `homeManagerModules.*`, `lib.*`, `packages.*`, `navi` / `naviHive`. `modules/parts.nix` declares supported systems and the `flake.lib` / `flake.homeManagerModules` option slots.
+
+## Option namespaces
+
+Project options live under `chiasson.*` only:
+
+| Prefix | For |
+|--------|-----|
+| `chiasson.system.*` | Machine policy — docker, flatpak, audio, gaming, deploy builder, … |
+| `chiasson.desktop.*` | GUI — compositors, DMS, wallpapers, display manager |
+| `chiasson.home.*` | Home Manager toggles (module exports are still `wisdom*`) |
+| `chiasson.users.*` | Catalog, `enabled`, `hostOverrides`, `extraModules` |
+| `chiasson.ssh.*` | SSH inventory |
+
+Leave upstream `services.*`, `networking.*`, `home.*`, etc. alone.
+
+## Module shape
+
+**NixOS leaf** — camelCase export, usually prefixed (`systemDocker`, `desktopNiri`):
+
+```nix
+{ ... }: {
+  flake.nixosModules.systemSomething = { config, lib, pkgs, ... }:
+  let cfg = config.chiasson.system.something;
+  in {
+    options.chiasson.system.something.enable = lib.mkEnableOption "…";
+    config = lib.mkIf cfg.enable { /* … */ };
+  };
+}
+```
+
+Aggregates: `nixosModules.system` and `nixosModules.desktop` import their leaves. Host configs import those stacks and set options — they shouldn't reimplement whole subsystems.
+
+**Home** — files under `modules/wisdom/`. Baseline is `homeManagerModules.wisdom` (`chiasson.home.enable`). Everything else is separate exports (`wisdomBrowsersZen`, …); enable on a host via `chiasson.users.extraModules.<user>` and the matching `chiasson.home.*.enable`.
+
+User apps / dotfiles → wisdom. Daemons, firewall, kernel → NixOS. Sometimes both (LocalSend: HM installs, `systemLocalsend` opens the firewall).
+
+**Odd exports**
+
+- `"client-services"` — shared setup for laptops/tablets/desktops (not the VMs). Turns on Bluetooth, lets Navi log in as `builder` to update the machine, enables printing and mounting USB drives, and sets SSH to password. Used on `t2mbp`, `14900k`, `ideapad`, `uConsole`. Skipped on `nix-server` and `r5500`.
+- `systemUconsoleKernelBuilder` — cross-build the uConsole kernel on x86_64, not for running on the Pi.
+- `systemFlatpak` — allowlist sync; skips heavy `flatpak update` when lists unchanged (`runHeavyMaintenanceEverySwitch`).
+
+**Desktop notes**
+
+- `chiasson.desktop.displayManager.variant`: `sddm` vs `dankgreeter` (DMS + Hyprland/Niri tends toward DankGreeter).
+- `desktopWallpapers` copies `inputs.wallpapers` into the store; override `chiasson.desktop.wallpapers.source` if needed.
+
+
+## Users
+
+User definitions live in `usersCatalogDefaults` (`modules/system/users/catalog-default.nix`) — olivier, server, builder, etc. Pick who exists on a host with `chiasson.users.enabled`.
+
+Passwords aren't in the repo. They're in `secrets/secrets.yaml` (encrypted with sops). Each host that has `olivier` must declare that secret and set `neededForUsers = true`; sops-nix decrypts it at boot, and the catalog points `hashedPasswordFile` at that file. That's why the catalog is a proper module instead of a static list — it needs `config.sops.secrets.…` at eval time.
+
+On a host:
+
+```nix
+chiasson.users.enabled = [ "olivier" ];
+chiasson.users.hostOverrides.<name> = { /* optional */ };
+chiasson.users.extraModules.olivier = [
+  self.homeManagerModules.wisdomTerminalsKitty
+  # …
+];
+```
+
+`usersHomeIntegration` turns that into `users.users` + HM. Don't hand-roll catalog users unless you're changing the users module itself.
+
+SSH: `sshInbound` on NixOS, outbound/rbw under `modules/ssh/home-manager/`.
+
+## Adding things
+
+**New NixOS leaf:** export `flake.nixosModules.whatever`, wire from `system/default.nix` or `desktop/default.nix` if it's global, or only from a host `configuration.nix` if it's not. `nix flake check`. Git-add new paths if eval uses the git tree.
+
+**New HM slice:** export `flake.homeManagerModules.wisdomFoo`, add the file to `imports` in `modules/wisdom/default.nix`, then wire `extraModules` + options on hosts that need it.
+
+**Derivations:** `let` inside a fragment, or `flake.packages` / `flake.lib` — not a bare `mkDerivation` file import-tree will try to load.
+
+**New host:** `hosts/<name>/default.nix` with `nixosSystem`, `configuration.nix` exporting `*Configuration`, hardware + `_private/` as needed, register in `modules/deploy/navi.nix` if it should be in the fleet.
+
+## When editing
+
+- `nix flake check` after touching `modules/`.
+- Stage/commit new files if the flake is read from git.
+- Small diffs; `mkEnableOption` + `mkIf` for toggles.
+- Cross-module deps: assertions or `mkDefault`, mention it in the option description.
+- New flake inputs in `flake.nix` with `follows` where versions should track nixpkgs.
+- `client-services` SSH defaults are for my LAN — don't copy to anything internet-facing without tightening.
+- If I'll forget the behavior in six months, update these docs in the same change.