Nix Language Guide

The Nix language is a pure, lazy, functional language used for package management and system configuration. Unlike traditional package managers, Nix treats packages as immutable values and builds them in isolation.

Why Nix?

Nix offers several unique advantages:

• Reproducibility: Every package is built in isolation with explicit dependencies

• Atomic upgrades and rollbacks: System changes are atomic and can be rolled back

• Multi-user package management: Different users can have different configurations

• Declarative system configuration: Your entire system is defined in code

"While Arch users are still fixing their broken systems after updates, NixOS users are happily rolling back to working configurations with a single command. It's like having a time machine for your OS!" 😉

The Nix Language Basics

# Basic variable declaration
let
  name = "example";
  version = "1.0";
in {
  inherit name version;
  fullName = "${name}-${version}";
}

Working with Packages

Installing Packages

# In configuration.nix
environment.systemPackages = with pkgs; [
  firefox
  vscode
  git
];

Creating Custom Packages

# Example of a simple package derivation
{ stdenv, fetchFromGitHub }:

stdenv.mkDerivation {
  pname = "my-package";
  version = "1.0.0";
  
  src = fetchFromGitHub {
    owner = "username";
    repo = "repo-name";
    rev = "v1.0.0";
    sha256 = "sha256-hash";
  };
  
  buildPhase = "make";
  installPhase = "make install";
}

Development Environments

Python Development

# shell.nix for Python development
{ pkgs ? import <nixpkgs> {} }:

pkgs.mkShell {
  buildInputs = with pkgs; [
    python39
    python39Packages.pandas
    python39Packages.numpy
    python39Packages.pytest
  ];
}

Go Development

# shell.nix for Go development
{ pkgs ? import <nixpkgs> {} }:

pkgs.mkShell {
  buildInputs = with pkgs; [
    go
    gopls
    go-tools
  ];
}

Rust Development

# shell.nix for Rust development
{ pkgs ? import <nixpkgs> {} }:

pkgs.mkShell {
  buildInputs = with pkgs; [
    rustc
    cargo
    rustfmt
    rust-analyzer
  ];
}

Adding Non-Packaged Software

Flatpak Integration

# Enable Flatpak support
services.flatpak.enable = true;

# Add Flathub repository
systemd.services.configure-flathub = {
  script = ''
    flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
  '';
  wantedBy = [ "multi-user.target" ];
};

Binary Packages

# Example of wrapping a binary
{ stdenv, makeWrapper, ... }:

stdenv.mkDerivation {
  name = "binary-wrapper";
  
  buildInputs = [ makeWrapper ];
  
  installPhase = ''
    mkdir -p $out/bin
    makeWrapper ${./binary} $out/bin/binary \
      --prefix PATH : ${stdenv.lib.makeBinPath [ dependencies ]}
  '';
}

Creating Packages from GitHub

# Example of packaging from GitHub source
{ lib, stdenv, fetchFromGitHub }:

stdenv.mkDerivation rec {
  pname = "example-package";
  version = "1.0.0";

  src = fetchFromGitHub {
    owner = "username";
    repo = pname;
    rev = "v${version}";
    sha256 = "sha256-hash"; # Replace with actual hash
  };

  meta = with lib; {
    description = "An example package";
    homepage = "https://github.com/username/example-package";
    license = licenses.mit;
    maintainers = with maintainers; [ yourusername ];
  };
}

Advanced Nix Functions

Nix functions are pure and support pattern matching, making them powerful tools for package management.

# Basic function syntax
name: "Hello ${name}"

# Function with multiple arguments
{ name, age }: {
  greeting = "Hello ${name}";
  isAdult = age >= 18;
}

# Function with default values
{ name ? "anonymous", age ? 0 }:
let
  greet = n: "Hello ${n}";
in {
  message = greet name;
  years = age;
}

"While Arch users are writing bash scripts to automate their system, NixOS users are writing pure functions that would make Haskell developers jealous!" 😄

Understanding Nix Modules

Modules are the building blocks of NixOS configuration. They're like LEGO pieces, but instead of building toys, you're building an unbreakable system (looking at you, Arch users)!

# Basic module structure
{ config, pkgs, lib, ... }: {
  options = {
    myService = {
      enable = lib.mkEnableOption "my cool service";
      port = lib.mkOption {
        type = lib.types.port;
        default = 8080;
        description = "Port to listen on";
      };
    };
  };

  config = lib.mkIf config.myService.enable {
    systemd.services.myService = {
      description = "My Cool Service";
      wantedBy = [ "multi-user.target" ];
      serviceConfig = {
        ExecStart = "${pkgs.myPackage}/bin/start --port ${toString config.myService.port}";
      };
    };
  };
}

"Arch users: 'I spent all weekend fixing my system after an update' NixOS users: 'I spent all weekend creating beautiful, composable modules'" 🎨

Deep Dive into Derivations

Derivations are the secret sauce of Nix. They're the recipes that tell Nix how to build packages.

# Advanced derivation example
{ lib
, stdenv
, fetchFromGitHub
, cmake
, boost
, openssl
, ...
}:

stdenv.mkDerivation rec {
  pname = "advanced-example";
  version = "2.0.0";

  src = fetchFromGitHub {
    owner = "example";
    repo = pname;
    rev = "v${version}";
    sha256 = "sha256-hash";
  };

  # Build-time dependencies
  nativeBuildInputs = [
    cmake
  ];

  # Runtime dependencies
  buildInputs = [
    boost
    openssl
  ];

  # Custom configure phase
  configurePhase = ''
    cmake . \
      -DCMAKE_BUILD_TYPE=Release \
      -DENABLE_TESTS=OFF
  '';

  # Custom build phase
  buildPhase = ''
    make -j $NIX_BUILD_CORES
  '';

  # Custom install phase
  installPhase = ''
    mkdir -p $out/bin
    cp bin/program $out/bin/
    
    # Install documentation
    mkdir -p $out/share/doc
    cp docs/* $out/share/doc/
  '';

  # Post-install checks
  doCheck = true;
  checkPhase = ''
    ./run-tests.sh
  '';

  # Package metadata
  meta = with lib; {
    description = "An advanced example package";
    homepage = "https://example.com";
    license = licenses.mit;
    maintainers = with maintainers; [ yourname ];
    platforms = platforms.unix;
  };
}

Advanced Module Composition

# Composing multiple modules
{ config, lib, ... }:

let
  cfg = config.myApp;
in {
  imports = [
    ./database.nix
    ./webserver.nix
    ./cache.nix
  ];

  options.myApp = {
    environment = lib.mkOption {
      type = lib.types.enum [ "development" "staging" "production" ];
      default = "development";
      description = "Application environment";
    };
  };

  config = lib.mkMerge [
    (lib.mkIf (cfg.environment == "production") {
      # Production-specific settings
    })
    (lib.mkIf (cfg.environment == "development") {
      # Development-specific settings
    })
  ];
}

"Arch users brag about their rolling releases. NixOS users roll their eyes and demonstrate atomic upgrades with rollbacks!" 🎯

Function Patterns and Best Practices

# Pattern matching in functions
let
  matchUser = { name, isAdmin ? false, ... }: 
    if isAdmin 
    then "Admin: ${name}"
    else "User: ${name}";
in {
  user1 = matchUser { name = "alice"; isAdmin = true; };
  user2 = matchUser { name = "bob"; };
}

# Higher-order functions
let
  compose = f: g: x: f (g x);
  double = x: x * 2;
  addOne = x: x + 1;
  doubleAndAddOne = compose addOne double;
in
  doubleAndAddOne 5  # Returns 11

"Why do Arch users have such good cardio? From running pacman -Syu and rushing to fix their system afterward! Meanwhile, NixOS users are relaxing with their deterministic builds." 🏃‍♂️

Advanced Derivation Techniques

Override and Overriding

let
  basePackage = pkgs.myPackage;
  customPackage = basePackage.override {
    enableFeature = true;
    extraFlags = [ "--with-optimization" ];
  };

  # Deep override
  superCustomPackage = basePackage.overrideAttrs (oldAttrs: {
    version = "2.0.0";
    src = fetchFromGitHub {
      # new source details
    };
    buildInputs = oldAttrs.buildInputs ++ [ pkgs.extraDependency ];
  });
in {
  inherit customPackage superCustomPackage;
}

"An Arch user and a NixOS user walk into a bar. The Arch user orders whatever's on tap. The NixOS user specifies the exact git commit of their preferred brew." 🍺

Why This Approach is Superior

1. Reproducibility: Every build is deterministic

2. Atomic Updates: No partial updates that can break your system

3. Rollbacks: Easy system state management

4. Isolation: Dependencies don't conflict

5. Development Environments: Perfect for DevOps and multi-language development

"Arch users spend their time reading wikis about how to fix their systems. NixOS users spend their time reading wikis about how to make their systems even more awesome!" 🎯

Best Practices

1. Always pin your dependencies versions

2. Use nix-shell for development environments

3. Document your derivations

4. Use nixfmt to format your Nix files

5. Leverage flakes for better reproducibility