# NixOS Configuration Guide

This NixOS configuration repository uses a modular, hierarchical import structure to manage system and home-manager configurations across multiple environments and desktop setups.

## Table of Contents

1. [Architecture Overview](#architecture-overview)
2. [Directory Structure](#directory-structure)
3. [How Import Wranglers Work](#how-import-wranglers-work)
4. [Switching Environments](#switching-environments)
5. [Configuration Layers](#configuration-layers)
6. [Modifying Configurations](#modifying-configurations)

---

## Architecture Overview

The configuration follows a **layered orchestrator pattern**:

```
flake.nix (entry point)
  ↓
configuration.nix (system orchestrator)
  ├─ hardware-configuration.nix (hardware specifics)
  ├─ modules/nixos/base/ (system-wide config)
  │   └─ default.nix (orchestrator)
  │       ├─ nix.nix
  │       ├─ boot.nix
  │       ├─ networking.nix
  │       ├─ users.nix
  │       ├─ services.nix
  │       ├─ programs.nix
  │       ├─ graphics.nix
  │       └─ packages.nix
  └─ modules/nixos/{i3wm,hyprland}/ (environment-specific)

mun.nix (home-manager orchestrator)
  ├─ modules/home/i3wm/default.nix (orchestrator)
  │   ├─ dunst.nix
  │   ├─ i3.nix
  │   ├─ kitty.nix
  │   ├─ neovim.nix
  │   ├─ nnn.nix
  │   ├─ picom.nix
  │   ├─ polybar.nix
  │   ├─ rofi.nix
  │   ├─ scripts.nix
  │   └─ xdg.nix
  └─ modules/home/hyprland/default.nix (orchestrator)
      └─ chernobyl/default.nix (orchestrator)
          ├─ dunst.nix
          ├─ fastfetch.nix
          ├─ hyprland.nix
          └─ kitty.nix
```

---

## Directory Structure

```
.
├── flake.nix                              # Flake inputs/outputs definition
├── flake.lock                             # Lock file for reproducibility
├── configuration.nix                      # Main system config (thin orchestrator)
├── hardware-configuration.nix             # Hardware-specific config (generated)
├── mun.nix                                # Home-manager user config (orchestrator)
├── modules/
│   ├── nixos/
│   │   ├── base/                          # Base system config (split modules)
│   │   │   ├── default.nix                # Orchestrator: imports all base modules
│   │   │   ├── nix.nix                    # Nix settings, flakes, substituters
│   │   │   ├── boot.nix                   # Boot loader, kernel, Plymouth
│   │   │   ├── networking.nix             # Hostname, NetworkManager, Bluetooth
│   │   │   ├── users.nix                  # User definitions
│   │   │   ├── services.nix               # System services (SSH, Pipewire, Printing, Ly)
│   │   │   ├── programs.nix               # System programs (Firefox, Zsh, Steam)
│   │   │   ├── graphics.nix               # GPU drivers, hardware acceleration
│   │   │   └── packages.nix               # System-wide packages
│   │   ├── i3wm/
│   │   │   └── default.nix                # X11, i3 window manager config
│   │   └── hyprland/
│   │       └── default.nix                # Wayland, Hyprland config
│   └── home/
│       ├── i3wm/
│       │   ├── default.nix                # Orchestrator: imports all i3wm home modules
│       │   ├── dunst.nix                  # Notification daemon (i3 config)
│       │   ├── i3.nix                     # i3 window manager config (keybinds, layout)
│       │   ├── kitty.nix                  # Terminal emulator (i3 config)
│       │   ├── neovim.nix                 # Text editor with LazyVim setup
│       │   ├── nnn.nix                    # File browser
│       │   ├── picom.nix                  # X11 compositor
│       │   ├── polybar.nix                # Status bar (i3 specific)
│       │   ├── rofi.nix                   # Application launcher
│       │   ├── scripts.nix                # Custom shell scripts
│       │   └── xdg.nix                    # XDG MIME type defaults
│       └── hyprland/
│           ├── default.nix                # Orchestrator: imports Hyprland rices
│           └── chernobyl/                 # "Chernobyl" Hyprland rice
│               ├── default.nix            # Orchestrator for chernobyl rice
│               ├── dunst.nix              # Notification daemon (Hyprland config)
│               ├── fastfetch.nix          # System info display
│               ├── hyprland.nix           # Hyprland window manager config
│               └── kitty.nix              # Terminal emulator (Hyprland config)
```

---

## How Import Wranglers Work

An "import wrangler" is a `default.nix` file that acts as a **local aggregator**, collecting all related configurations into one place for easy management. This pattern appears at multiple levels:

### Level 1: Base System Configuration

**File:** `modules/nixos/base/default.nix`

```nix
{ ... }:

{
  imports = [
    ./nix.nix
    ./boot.nix
    ./networking.nix
    ./users.nix
    ./services.nix
    ./programs.nix
    ./graphics.nix
    ./packages.nix
  ];

  system.stateVersion = "25.11";
}
```

**Purpose:** Groups all foundational system configurations (boot, networking, users, services, packages) into a single import point. When you need to add a base system feature, you either:
- Add it to an existing module file
- Create a new module (e.g., `firewall.nix`) and add it to this import list

**Benefits:**
- Single import in `configuration.nix`: `./modules/nixos/base`
- All base modules are in one place; easy to see what's included
- New base modules are simply added to the imports list

### Level 2: Environment-Specific System Configuration

**Files:** `modules/nixos/i3wm/default.nix`, `modules/nixos/hyprland/default.nix`

These are currently thin wrappers but follow the same pattern. To extend them (e.g., add environment-specific services or packages), you would create sub-modules:

```nix
# Example expansion of modules/nixos/i3wm/default.nix
{ ... }:

{
  imports = [
    ./xserver.nix        # X11-specific settings
    ./i3.nix            # i3 window manager
    ./keyboard.nix      # Czech keyboard layout
  ];
}
```

### Level 3: Home-Manager Orchestration

**File:** `modules/home/i3wm/default.nix`

```nix
{ ... }:

{
  imports = [
    ./dunst.nix
    ./i3.nix
    ./kitty.nix
    ./neovim.nix
    ./nnn.nix
    ./picom.nix
    ./polybar.nix
    ./rofi.nix
    ./scripts.nix
    ./xdg.nix
  ];
}
```

**Purpose:** All i3wm-specific home-manager modules (dunst, i3 keybinds, polybar, etc.) are collected here. This is imported once in `mun.nix`, rather than importing 10 separate files.

**Benefits:**
- One line in `mun.nix`: `./modules/home/i3wm/default.nix`
- All i3 home configs are clearly grouped
- Easy to switch entire environments with a single comment/uncomment

### Level 4: Multi-Rice Support (Hyprland)

**File:** `modules/home/hyprland/default.nix`

```nix
{ ... }:

{
  imports = [
    #./default.nix              # main hyprland rice (future)
    ./chernobyl/default.nix     # chernobyl hyprland rice
  ];
}
```

**File:** `modules/home/hyprland/chernobyl/default.nix`

```nix
{ ... }:

{
  imports = [
    ./dunst.nix
    ./fastfetch.nix
    ./hyprland.nix
    ./kitty.nix
  ];
}
```

**Purpose:** Supports multiple visual rices/themes for the same window manager. The parent orchestrator selects which rice to use.

**Benefits:**
- Scale to many rices easily (add `./cyberpunk/default.nix`, `./nord/default.nix`, etc.)
- Each rice has its own folder with consistent structure
- Switch rices by commenting/uncommenting in the parent orchestrator

---

## Switching Environments

### Switch from i3wm to Hyprland

Edit **two files**:

#### 1. System Configuration (`configuration.nix`)

```nix
{ config, lib, pkgs, ... }:

{
  imports = [
    ./hardware-configuration.nix
    ./modules/nixos/base
    
    # === Environment Choice ===
    # Uncomment one of the following to select your environment:
    #./modules/nixos/i3wm      # ← comment this
    ./modules/nixos/hyprland   # ← uncomment this
  ];
}
```

#### 2. Home-Manager Configuration (`mun.nix`)

```nix
{ config, lib, pkgs, ... }:

{
  imports = [
    #./modules/home/i3wm/default.nix      # ← comment this
    ./modules/home/hyprland/default.nix   # ← uncomment this
  ];
  
  # ... rest of mun.nix
}
```

#### 3. Rebuild

```bash
sudo nixos-rebuild switch
```

---

## Configuration Layers

The configuration is organized in **four distinct layers**:

### 1. **System-Wide Base (`modules/nixos/base/`)**

Applied to **all environments**.

**Includes:**
- Nix settings (flakes, substituters)
- Boot configuration (GRUB, EFI, kernel)
- Networking (hostname, NetworkManager, Bluetooth)
- Users (mun user definition)
- System services (SSH, Pipewire, Printing, Ly display manager)
- System programs (Firefox, Zsh, Steam)
- Graphics drivers (Intel VAAPI, hardware acceleration)
- System packages (Neovim, Git, TeX Live, RetroArch, etc.)

**Modify by:** Editing existing files in `base/` or creating new ones and adding them to `base/default.nix`.

### 2. **Environment-Specific System (`modules/nixos/{i3wm,hyprland}/`)**

Applied to **one environment at a time** (X11 vs Wayland).

**i3wm includes:**
- X11 enable
- i3 window manager
- Keyboard layout (Czech)
- Display manager session

**Hyprland includes:**
- X11 disable
- Hyprland enable
- XDG portal for Wayland
- Qt6 Wayland support
- Keyboard layout (Czech)

**Modify by:** Editing the respective `default.nix` or creating sub-modules.

### 3. **Home-Manager User-Wide Config (`mun.nix`)**

Configuration applied to user `mun` only.

**Includes:**
- SSH setup
- Shell configuration (Zsh with oh-my-zsh)
- Environment variables
- Gnome-keyring service
- User packages (Rust tools, Discord, utilities)
- Environment-specific home-manager orchestrator import

**Modify by:** Editing `mun.nix` directly or adding packages to the `packages` list.

### 4. **Environment-Specific Home-Manager (`modules/home/{i3wm,hyprland}/`)**

Applied to **one environment at a time**.

**i3wm includes:**
- i3 keybindings and layout
- Polybar status bar
- Dunst notifications
- Picom compositor
- Rofi launcher
- NeoVim with LazyVim
- Kitty terminal
- Custom scripts
- XDG MIME type defaults

**Hyprland (chernobyl rice) includes:**
- Hyprland config
- Dunst notifications
- Kitty terminal
- Fastfetch system info

**Modify by:** Editing the respective module files or adding new ones to the orchestrator `default.nix`.

---

## Modifying Configurations

### Add a New System Package

**File:** `modules/nixos/base/packages.nix`

```nix
environment.systemPackages = with pkgs; [
  # ... existing packages ...
  my-new-package  # ← add here
];
```

### Add a New Base System Service

**File:** `modules/nixos/base/services.nix` or create `modules/nixos/base/firewall.nix`

If adding firewall rules, create a new file:

```nix
# modules/nixos/base/firewall.nix
{ config, lib, pkgs, ... }:

{
  networking.firewall.allowedTCPPorts = [ 80 443 ];
}
```

Then add to orchestrator:

```nix
# modules/nixos/base/default.nix
{ ... }:

{
  imports = [
    ./nix.nix
    ./boot.nix
    ./networking.nix
    ./users.nix
    ./services.nix
    ./programs.nix
    ./graphics.nix
    ./packages.nix
    ./firewall.nix  # ← add here
  ];

  system.stateVersion = "25.11";
}
```

### Add an i3wm Home-Manager Module

**File:** `modules/home/i3wm/my-new-config.nix`

```nix
{ config, pkgs, ... }:

{
  # Your home-manager config here
}
```

Then add to orchestrator:

```nix
# modules/home/i3wm/default.nix
{ ... }:

{
  imports = [
    ./dunst.nix
    ./i3.nix
    # ... other modules ...
    ./my-new-config.nix  # ← add here
  ];
}
```

### Add a New Hyprland Rice

Create a new directory:

```bash
mkdir modules/home/hyprland/cyberpunk
```

Add files:

```nix
# modules/home/hyprland/cyberpunk/default.nix
{ ... }:

{
  imports = [
    ./dunst.nix
    ./hyprland.nix
    ./kitty.nix
  ];
}
```

Update parent orchestrator:

```nix
# modules/home/hyprland/default.nix
{ ... }:

{
  imports = [
    #./default.nix
    ./chernobyl/default.nix
    #./cyberpunk/default.nix  # ← uncomment to use
  ];
}
```

---

## Rebuilding Your System

After making changes:

```bash
# Switch to new system configuration
sudo nixos-rebuild switch

# Or, test first (doesn't activate)
sudo nixos-rebuild test

# Show what changed
sudo nixos-rebuild dry-run
```

To edit and rebuild in one step:

```bash
# If you have the 'edit' alias from mun.nix
edit
sudo nixos-rebuild switch
```

---

## Key Principles

1. **One Import Per Layer:** Each `default.nix` orchestrator imports related modules, reducing clutter in parent files.

2. **Separation of Concerns:** System config (nixos/) is separate from user config (home/); base is separate from environment-specific.

3. **Easy Environment Switching:** Change environments by commenting one line in `configuration.nix` and `mun.nix`.

4. **Scalability:** Adding new features (base services, home modules, rices) follows a consistent pattern of creating a file + adding it to the orchestrator.

5. **Clarity:** Each file has a clear purpose; finding where to modify something is straightforward.

---

## Example Workflow

### Goal: Add Firefox configuration to i3wm

1. Create `modules/home/i3wm/firefox.nix`:
   ```nix
   { config, pkgs, ... }:

   {
     programs.firefox = {
       enable = true;
       profiles.mun = {
         settings = {
           "browser.startup.homepage" = "about:home";
         };
       };
     };
   }
   ```

2. Add to orchestrator in `modules/home/i3wm/default.nix`:
   ```nix
   imports = [
     ./dunst.nix
     ./firefox.nix  # ← add here
     ./i3.nix
     # ... rest
   ];
   ```

3. Rebuild:
   ```bash
   sudo nixos-rebuild switch
   ```

Done! Firefox is now configured for the i3wm environment.

---

## Troubleshooting

### "Module not found" error

Check that all imports in `default.nix` files reference correct file paths. Use absolute paths from the module directory:
- `./nix.nix` ✓ (correct)
- `../base/nix.nix` ✓ (correct, relative to parent)
- `/absolute/path/nix.nix` ✗ (avoid; use relative)

### Environment not loading after switch

Ensure **both** `configuration.nix` and `mun.nix` have the same environment enabled (not one i3wm and one hyprland).

### Syntax errors in .nix files

Use `nix flake check` to validate:
```bash
nix flake check
```

---

## References

- [NixOS Manual - Configuration](https://nixos.org/manual/nixos/stable/)
- [Home Manager Manual](https://nix-community.github.io/home-manager/)
- [Nix Language](https://nixos.wiki/wiki/Nix_language)