Variables Reference

Complete reference for all available configuration variables in variables.nix.

Overview

The variables.nix file is the central configuration hub for NullOS. It contains high-level settings that customize your system without diving into Nix module details.

Location: Root of NullOS directory
Template: variables.nix.example
Git Status: Ignored (add to .gitignore for privacy)

User Configuration

`username`

Type: String
Required: Yes
Example: "nullstring"

Your system username. Used for:

User account creation
Home directory path (/home/${username})
Home Manager configuration
Git commit author (if not overridden)

username = "yourusername";

`gitUsername`

Type: String
Required: Yes
Example: "NullString"

Your Git commit author name.

gitUsername = "Your Name";

`gitEmail`

Type: String
Required: Yes
Example: "you@example.com"

Your Git commit email address.

gitEmail = "you@example.com";

System Configuration

`hostname`

Type: String
Required: Yes
Example: "nslapt" or "nspc"

System hostname. Must match the configuration name in flake.nix.

Available Configurations:

nslapt - Laptop configuration
nspc - Desktop configuration

hostname = "nslapt";

Note: When building, use: sudo nixos-rebuild switch --flake .#nslapt

`system`

Type: String
Required: Yes
Default: "x86_64-linux"

System architecture. Currently only x86_64 Linux is supported.

system = "x86_64-linux";

Localization

`timeZone`

Type: String
Required: Yes
Example: "Europe/London" or "America/New_York"

System timezone. Find your timezone:

timedatectl list-timezones | grep -i london

timeZone = "Europe/London";

`locale`

Type: String
Required: Yes
Example: "en_GB.UTF-8" or "en_US.UTF-8"

System locale for language and formatting.

locale = "en_GB.UTF-8";

`keyboardLayout`

Type: String
Required: Yes
Example: "gb", "us", "de", "fr"

X11/Wayland keyboard layout.

keyboardLayout = "gb";

`consoleKeyMap`

Type: String
Required: Yes
Example: "uk", "us", "de", "fr"

Console (TTY) keyboard layout.

consoleKeyMap = "uk";

Applications

`terminal`

Type: String
Required: Yes
Default: "ghostty"

Default terminal emulator executable name.

Available Options:

"ghostty" - Modern GPU-accelerated terminal
"kitty" - Fast, feature-rich terminal
"alacritty" - Lightweight GPU terminal

terminal = "ghostty";

`browser`

Type: Package
Required: Yes
Example: pkgs.brave, pkgs.firefox, pkgs.chromium

Default web browser package.

browser = pkgs.brave;  # or pkgs.firefox, pkgs.chromium, etc.

Graphics Configuration

`useNvidiaPrime`

Type: Boolean
Required: Yes
Default: true (for hybrid graphics laptops)

Enable NVIDIA PRIME for hybrid graphics (Intel + NVIDIA).

true - Enable NVIDIA PRIME offload
false - Disable PRIME (single GPU systems)

useNvidiaPrime = true;

When to use true:

Laptops with Intel CPU + NVIDIA GPU
Want to use integrated graphics by default
Want option to run apps on NVIDIA when needed

When to use false:

Desktop with only NVIDIA GPU
Desktop with only Intel/AMD GPU
Single GPU laptops

`intelBusId`

Type: String
Required: If useNvidiaPrime = true
Example: "PCI:0:2:0"

PCI bus ID for Intel integrated GPU.

How to find:

nix-shell -p pciutils --run "lspci | grep VGA"

Output example:

00:02.0 VGA compatible controller: Intel Corporation ...

Convert 00:02.0 to PCI:0:2:0

intelBusId = "PCI:0:2:0";

`nvidiaBusId`

Type: String
Required: If useNvidiaPrime = true
Example: "PCI:2:0:0" or "PCI:1:0:0"

PCI bus ID for NVIDIA GPU.

How to find:

nix-shell -p pciutils --run "lspci | grep -i nvidia"

Output example:

02:00.0 VGA compatible controller: NVIDIA Corporation ...

Convert 02:00.0 to PCI:2:0:0

nvidiaBusId = "PCI:2:0:0";

Display Configuration

`extraMonitorSettings`

Type: Multi-line String
Required: No
Default: ""

Hyprland monitor configuration. Override auto-detection.

Format:

monitor = OUTPUT, RESOLUTION@REFRESH, POSITION, SCALE

Examples:

Single monitor (laptop):

extraMonitorSettings = "
  monitor = eDP-1, 1920x1080@60, auto, 1
  ";

Dual monitors (desktop):

extraMonitorSettings = "
  monitor = DP-1, 2560x1440@144, 0x0, 1
  monitor = HDMI-A-1, 1920x1080@60, 2560x0, 1
  ";

Triple monitors:

extraMonitorSettings = "
  monitor = DP-1, 2560x1440@144, 0x0, 1
  monitor = DP-2, 1920x1080@60, 2560x0, 1
  monitor = DP-3, 1920x1080@60, 2560x1080, 1
  ";

Find monitor names:

hyprctl monitors

Leave empty for auto-detection:

extraMonitorSettings = "";

Theming

`stylixImage`

Type: Path
Required: Yes
Example: wallpapers/screen.jpg

Path to wallpaper image used for Stylix theming.

Stylix generates a color scheme from this image and applies it system-wide.

stylixImage = wallpapers/mywall.jpg;

Supported formats:

JPEG (.jpg, .jpeg)
PNG (.png)
WebP (.webp)

Tips:

Images with distinct colors work best
Place wallpapers in wallpapers/ directory
Use relative path from flake root

Desktop Environment

`waybarConfig`

Type: Path
Required: Yes
Default: home/waybar/default.nix

Path to Waybar configuration file.

waybarConfig = home/waybar/default.nix;

You can create custom Waybar configs:

waybarConfig = home/waybar/custom-waybar.nix;

`animationSet`

Type: Path
Required: Yes
Default: home/hyprland/animations-end4.nix

Path to Hyprland animation configuration.

animationSet = home/hyprland/animations-end4.nix;

Available options:

Create your own in home/hyprland/
Modify existing animation files
Disable animations entirely

Services

`resticRepository`

Type: String
Required: Only if using backups
Example: "sftp:user@host:/backups/nslapt"

Restic backup repository location.

Supported backends:

Local:

resticRepository = "/mnt/backup";

SFTP:

resticRepository = "sftp:user@server.com:/backups";

S3:

resticRepository = "s3:s3.amazonaws.com/bucket-name";

B2:

resticRepository = "b2:bucket-name";

Note: Also configure password file in modules/services/backup.nix

Hardware Support

`printEnable`

Type: Boolean
Required: Yes
Default: true

Enable printing support (CUPS).

printEnable = true;  # Enable printers
printEnable = false; # Disable printers

`printDrivers`

Type: List of Packages
Required: If printEnable = true
Example: [ pkgs.hplip pkgs.gutenprint ]

Printer driver packages.

printDrivers = [ ];  # Auto-detect
printDrivers = [ pkgs.hplip ];  # HP printers
printDrivers = [ pkgs.gutenprint pkgs.epson-escpr ];  # Multiple drivers

Common drivers:

pkgs.hplip - HP printers
pkgs.gutenprint - Canon, Epson, etc.
pkgs.epson-escpr - Epson ESC/P-R
pkgs.brlaser - Brother laser

`add_rtl8852cu`

Type: Boolean
Required: No
Default: false

Add RTL8852CU WiFi driver (for specific USB WiFi adapters).

add_rtl8852cu = false;  # Don't need driver
add_rtl8852cu = true;   # Add RTL8852CU driver

When to enable:

You have an RTL8852CU USB WiFi adapter
WiFi not working out-of-box

Complete Example

Here's a complete example variables.nix:

{ nixpkgs, ... }:
let
  pkgs = import nixpkgs { system = "x86_64-linux"; };
in
{
  username = "alice";
  hostname = "nslapt";
  system = "x86_64-linux";

  gitUsername = "Alice Smith";
  gitEmail = "alice@example.com";

  terminal = "ghostty";
  browser = pkgs.firefox;

  keyboardLayout = "us";
  consoleKeyMap = "us";

  timeZone = "America/New_York";
  locale = "en_US.UTF-8";

  useNvidiaPrime = true;
  intelBusId = "PCI:0:2:0";
  nvidiaBusId = "PCI:1:0:0";

  stylixImage = wallpapers/nord-mountains.jpg;
  waybarConfig = home/waybar/default.nix;

  animationSet = home/hyprland/animations-end4.nix;

  resticRepository = "sftp:alice@backup.example.com:/backups/laptop";

  extraMonitorSettings = "
    monitor = eDP-1, 1920x1080@144, auto, 1
    ";

  printEnable = true;
  printDrivers = [ pkgs.hplip ];

  add_rtl8852cu = false;
}

Validation

After editing variables.nix, validate with:

nix flake check

Build without switching:

sudo nixos-rebuild build --flake .#yourhostname

Next Steps

Customization Guide - How to use these variables
Per Machine Config - Managing multiple machines
Installation - Setting up variables during install

Variables Reference

Variables Reference

Overview

User Configuration

username

gitUsername

gitEmail

System Configuration

hostname

system

Localization

timeZone

locale

keyboardLayout

consoleKeyMap

Applications

terminal

browser

Graphics Configuration

useNvidiaPrime

intelBusId

nvidiaBusId

Display Configuration

extraMonitorSettings

Theming

stylixImage

Desktop Environment

waybarConfig

animationSet

Services

resticRepository

Hardware Support

printEnable

printDrivers

add_rtl8852cu

Complete Example

Validation

Next Steps

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Clone this wiki locally

`username`

`gitUsername`

`gitEmail`

`hostname`

`system`

`timeZone`

`locale`

`keyboardLayout`

`consoleKeyMap`

`terminal`

`browser`

`useNvidiaPrime`

`intelBusId`

`nvidiaBusId`

`extraMonitorSettings`

`stylixImage`

`waybarConfig`

`animationSet`

`resticRepository`

`printEnable`

`printDrivers`

`add_rtl8852cu`