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Set up Nix on macOS using flakes, nix-darwin and home-manager

Created at: 2024-03-03 19:37

Updated at: 2024-07-07 19:43 (74f3d3e)

Reading time: 6 min read (1099 words)

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#nix
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About three years ago, I started using NixOS on my personal laptop. In those days, I needed a config that would allow me to have a stable system, that could be reproducible over all my machines, and that would allow me to have a development environment that would be easy to maintain and to share with others. NixOS comes to fit all these requirements.

But, since I started using a MacBook Pro (2022), I do not feel the necessity of using the Nix package manager, since I can use Homebrew to install all the packages that I need and have some kind of reproducibility with shell scripts. But, for some needs, I would like to use Nix again on my macOS now, and this blog post will be about how to set up Nix on macOS like me.

Installing Nix on macOS

Installing Nix on macOS is easy. You can use the following command to install Nix on your machine:

curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install

This command installs the Nix package manager based on the DeterminateSystem/nix-installer, based on the explanation by the Zero to Nix, it gives better error messages, an installation plan (like Terraform), and other cool features that bring a better installation experience for you.

Just follow the step by step of the installation flow and everything will be fine.

Creating the flake file

After installing Nix, you can create a flake.nix file that will be the entry point for your entire Nix configuration on your machine. This file will be used to define the packages that you want to install, the system configuration, and the home-manager configuration.

{
  description = "Nix configuration";
 
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs";
 
    nix-darwin.url = "github:lnl7/nix-darwin/master";
    nix-darwin.inputs.nixpkgs.follows = "nixpkgs";
 
    home-manager.url = "github:nix-community/home-manager";
    home-manager.inputs.nixpkgs.follows = "nixpkgs";
  };
 
  outputs = inputs @ { self, ... }: let
    nixpkgsConfig = {
      config.allowUnfree = true;
    };
  in {
 
  };
}

This is the basic structure of my flake.nix, it defines all the inputs that I will need to use in my configuration, they are:

  • nixpkgs: The main NixOS/Nixpkgs repository, that will be used to define the packages that I want to install on my machine.
  • nix-darwin: The nix-darwin repository. It brings all modules to configure your macOS system using a declarative way.
  • home-manager: The home-manager repository. It brings all modules to configure your user environment using a declarative way.

Configuring nix-darwin

After creating the flake.nix file, you can configure the nix-darwin module. You will need to create a darwinConfigurations field on the outputs of your flake.nix file, and add the hostname of your machine with the darwinSystem function.

{
  # ...
 
  outputs = inputs @ { self, nix-homebrew, home-manager ... }: let
    nixpkgsConfig = {
      config.allowUnfree = true;
    };
  in {
    darwinConfigurations = let
      inherit (inputs.nix-darwin.lib) darwinSystem;
    in {
      machine = darwinSystem {
        system = "aarch64-darwin";
 
        specialArgs = { inherit inputs; };
 
        modules = [
          ./hosts/mbp/configuration.nix
          inputs.home-manager.darwinModules.home-manager
          {
            nixpkgs = nixpkgsConfig;
 
            home-manager.useGlobalPkgs = true;
            home-manager.useUserPackages = true;
            home-manager.users.noghartt = import ./home/home.nix;
          }
        ];
      };
    };
  };
}

In that case, what I’m doing is: creating a new configuration called machine on the darwinConfigurations systems, and declaring some specific properties of that given system, they are:

  • The system of that machine is aarch64-darwin, which is the system of the new Apple Silicon Macs (MacBook Pro M1).
  • The specialArgs field is used to pass the inputs to the darwinSystem function. All modules are functions that accept some arguments, the specialArgs field lets you pass new arguments for all these imported modules.
  • The modules field is used to define the modules that will be used to configure the system. In that case, I’m using the configuration.nix file to define my system configuration, the home-manager module to configure the user environment, the homebrew.nix file to install all the packages that I want to install using Homebrew, and the home.nix file to configure my user environment using home-manager.

Configuring my system

The configuration.nix file is used to define some system configurations related to my MacBook Pro, like user home dir, some extra options related to Nix binaries, and other system-related configurations that you want to declare. In my case, I wrote the following configuration.nix:

_:
 
{
  services.nix-daemon.enable = true;
 
  users.users.noghartt = {
    home = "/Users/noghartt";
  };
 
  nix.extraOptions = ''
    auto-optimise-store = true
    experimental-features = nix-command flakes
    extra-platforms = x86_64-darwin aarch64-darwin
  '';
 
  homebrew = {
    enable = true;
 
    casks = [
      "discord"
      "visual-studio-code"
    ];
  };
}

Configuring the home-manager

The home.nix file is used to define the user environment configurations using the home-manager. In my case, I wrote just a simple home.nix file that installs some packages for me. It is like a configuration.nix file but for the user environment.

{ pkgs, ... }:
 
{
  home.stateVersion = "23.11";
 
  home.packages = with pkgs; [
    htop
    curl
    coreutils
    jq
  ];
 
  programs.zsh = {
    enable = true;
 
    shellAliases = {
      ls = "ls --color";
    };
  };
}

With that configuration, I can install the initial packages that I want to use on my machine using Nix, and gives me the powerful ability of reproducibility in a declarative way.

Building and activating the configuration

After creating all the files, you can build and activate the configuration using the following. You just need to run two specific commands to build and activate the configuration on your machine:

1. Building the configuration

nix build .#darwinConfigurations.machine.config.system

It will build the configuration of your machine targeting the darwinConfigurations.machine outputs. Do not forget of changing the machine of the given name of your system configuration.

2. Activating the configuration

./result/sw/bin/darwin-rebuild switch --flake .

It will activate the configuration of your machine using the darwin-rebuild command. It will switch the configuration of your machine to the new configuration that you have built.

Conclusion

In this blog post, I showed how to set up Nix on macOS using flakes, nix-darwin, and home-manager like I do. I hope that this blog post can help you set up your configuration and let you use Nix on your machine too.

I really love how the Nix package manager works, and I think that it is a great tool to use on your machine since it gives you a lot of power to manage your system and your user environment. You really should give it a try.

If you want to see my configuration, you can check it out on my repository, it’s all open source, feel free to use it as a base for your configuration if you want.

If you have any questions, feel free to ask me on Twitter or send me an email. I will be glad to help you with your doubts.

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