dotnix

Declarative system configuration used on my 2018 Intel Macbook Pro.

$ nix-info -m && date
 - system: `"x86_64-darwin"`
 - host os: `Darwin 23.4.0, macOS 10.16`
 - multi-user?: `no`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.19.2`
 - nixpkgs: `not found`

Mon Mar 18 09:12:30 PDT 2024

• dotnix
  • What The Hell Is Going On Here!?
    • System Configuration with Nix
    • Understanding dotnix
  • Do
    • Installation
    • Modifying the System Configuration
    • Updating the System Configuration
  • Resources

What The Hell Is Going On Here!?

Check out my blog post Fearless Tinkering with Nix for an introduction to and conceptual overview of Nix covering:

• what problems nix solves
• the architecture of nix and the software engineering philosophies that shape it
• ways that nix and its ecosystem can be used

System Configuration with Nix

NixOS allows users to define their entire system configuration in a declarative manner via the Nix expression language. This includes specifying packages, services, users, and other system settings. The declarative nature of NixOS ensures that the system configuration is version-controllable, reproducible, and easy to share. It also simplifies system administration by providing a single source of truth for the entire system state.

Outside of NixOS, declarative system configuration can be achieved on MacOS through various Nix-based tools like home-manager and nix-darwin. These tools work with both standard and flake-based approaches:

System Configuration	Platforms	Configuration File	Configuration Options	Notes
NixOS	NixOS	configuration.nix	Available in Manual or NixOS Options Search
Home-Manager	NixOS, Linux, MacOS	home.nix	accounts, home, launchd, nix, programs, services, systemd, targets.darwin, wayland, xdg, xsession	Can also be configured as NixOS module or nix-darwin module
Nix-Darwin	MacOS	darwin-configuration.nix	enviroment, homebrew, launchd, networking, nix, programs, services, system, users	Can manage homebrew package installations (ex. brew install foo)

Understanding dotnix

dotnix (this repo) is a flake-based system configuration for my machine powered by both Nix-Darwin and Home-Manager.

File	Purpose	Notes
darwin.nix	My system configuration via nix-darwin including: • packages from nixpkgs • packages from homebrew • MacOS settings (dock, scroll direction, etc) ...and more	• Nix-Darwin Options - pre-defined configurations available with nix-darwin • NixPkgs - package repository + binary cache with 100k+ available packages
home.nix	My system configuration via home-manager including: • apps (1Password, Firefox, VSCode) • dev settings (.git, .bashrc) • CLI tools (bat, fzf, jq) ...and more	• Home-Manager Manual - tool for declaratively managing system configuration, dotfiles, etc • Home-Manager Options & Options Search - pre-defined configurations available with home-manager
flake.nix	Takes Nix expressions as input, then output things like package definitions, development environments, or, as is the case here, system configurations. For this specific repository, we can think of it as wrapping darwin.nix and home.nix in order to provide it pinned dependencies and manage the outputs.	• Zero to Nix Glossary • xeiaso's Nix Flake Guides
flake.lock	Pins dependencies used in flake inputs
bin/apply-system.sh	Script to initialize and apply system configuration. Also downloads homebrew binary outside of nix, and configures default shell	Simple nix run nix-darwin -- switch invocation (same as running darwin-rebuild switch)
bin/apply-system.sh	Script to apply system configuration	Simple nix run nix-darwin -- switch invocation (same as running darwin-rebuild switch)
bin/update-system.sh	Script to update dependencies	Simple nix flake update invocation

---

Software installed with dotnix is specified in following ways:

• Home-Manager Options
  • Via programs.* in home.nix
• Nixpkgs Package Set
  • Via home.packages in home.nix, corresponding to nixpkgs release at flake.nix:inputs.nixpkgs.url
• Flake Inputs
  • Via inputs in flake.nix and pinned in flake.lock

System-wide nix settings are specified in home.nix under the following declarations:

• nix.package
  • Determines which version of nix is used
    • Has matching declaration under home.packages.config.nix.package
• home.sessionVariables
  • Environment variables set at login
• nix.settings
  • Replaces configuration that's usually found at /etc/nix/nix.conf
  • Sets feature flags, binary cache keys and locations, etc
• nix.registry
  • Replaces configuration that's usually found at /etc/nix/registry.json
  • Same as default found at https://github.com/NixOS/flake-registry

    • "The flake registry serves as a convenient method for the Nix CLI to associate short names with flake URIs, such as linking nixpkgs to github:NixOS/nixpkgs/nixpkgs-unstable."

Do

Installation

1. Install nix

Follow the Zero-to-Nix Quickstart Guide for a flake-based nix installation.

2. Setup dotnix repo

$ mkdir -p ~/.config
$ cd ~/.config
$ git clone https://github.com/hkscarf/dotnix

FIXME TODO - Need to describe configuring. Replacing hostname, user, home dir, etc

3. Apply system configurations

$ cd ~/.config/dotnix/
$ ./bin/init-system.sh

Modifying the System Configuration

1. Modify configuration files

For example, add a new package to install in darwin.nix or move to a newer release of nixpkgs in flake.nix.

2. Apply system configurations

$ cd ~/.config/dotnix/
$ ./bin/apply-system.sh

Updating the System Configuration

1. Update dependencies in flake.lock

$ cd ~/.config/dotnix/
$ ./bin/update-system.sh

2. Apply system configurations

$ cd ~/.config/dotnix/
$ ./bin/apply-system.sh

Resources

Declarative macOS Configuration - Using nix-darwin and home-manager: https://xyno.space/post/nix-darwin-introduction

Setting up Nix on macOS: https://davi.sh/til/nix/nix-macos-setup/

Switching to nix-darwin and Flakes: https://evantravers.com/articles/2024/02/06/switching-to-nix-darwin-and-flakes/