I recently bought a new MacBook, and instead of manually installing everything for the nth time, I decided to go down the path of using Nix and nix-darwin to codify my dev machine configuration. If you're curious, let's dive in.
What is Nix?
Nix is a few things which I would break down into three categories:
- A configuration and build system referred to as "Nix".
- A configuration language, confusingly also referred to as "Nix".
- A package manager wherein the official packages are referred to as "nixpkgs".
First and foremost, Nix is a configuration system for describing declaratively how your system should be configured. This includes things like packages, applications, and shell configuration, but can even include OS settings like your preferred scroll direction (natural scrolling disabled of course, for the sophisticated among us). If you've ever used something like Terraform or CloudFormation to set up your infrastructure, then in this context you might think of Nix as being like Terraform for your personal machine. When you "build" a version of your system configuration, Nix produces a "generation", which conceptually can be thought of as a deterministic snapshot of your system given the current configuration.
Second, the name "Nix" is also used (confusingly) to refer to the underlying configuration language itself that the configuration files are written in. This language is a declarative scripting language which is used to configure your system. In my experience it was relatively easy to get started with. The documentation is great, and there are a number of existing examples to work from.
Finally, Nix is a package manager. It has an official repository of packages called "nixpkgs" which you can browse here. When you define your configuration, you'll likely specify packages which will be sourced from nixpkgs. For example, things like git, or zsh, or python.
What is nix-darwin?
As my personal computer is running macOS, I am also using nix-darwin, which is a set of modules specifically for configuring macOS. It allows you (among other things) to modify operating system settings like the dock, hot corners, dark mode, etc. Not every single item within "System Settings" is supported yet, but it gets you most of the way there.
Conclusion
Ok, so that's a high-level overview of Nix, but why bother with any of that? For myself, I'd break it down as follows:
Pros
- Improved auditability. I can more easily see at a glance what is installed on my system. No more forgetting about some random package I installed 6 months ago and never use anymore!
- If something goes wrong, rollbacks with nix are super easy. If I break something critical, I can always roll back to a previous version of my system.
- Peace of mind that I could blow away my entire machine and start over quickly if needed.
Cons
- There was some initial investment required to get my system set up in the way I like. But I only needed to do this once!
- There was some learning curve in ramping up on Nix the language.
- GUI apps on macOS are not well supported, so you still need to use homebrew for these. You can at least configure which homebrew casks should be installed on the system via nix-darwin.
- Ideally, every single macOS system setting would be configurable with nix-darwin, but that's not true (yet).
Using Nix for my dev machine has been working great for me so far, and I'm now fully nix-pilled. You can check out my configuration here.
We could go deeper down the rabbit hole and talk in more detail about how Nix works under the hood. Or we could speak to more of the Nix ecosystem like home-manager, flakes, or NixOS; but I'll stop here for now. 🙃