This article is part of my personal journey on Nix. This system is quite powerful and complex, so you might find some misconceptions here. I will update these articles as I get more proficient on it 😊

One of the Nix advantages is the ability to install it in different environments. For example, you can add Nix to your macOS device or install a fresh new machine with NixOS. This powerful duality, also increases the complexity to understand Nix basics. Some documentation refers to certain files that are mainly related to one of the installation formats.

This is the case of configuration.nix and nix.conf.

NixOS defines the operating system configuration declaratively. Instead of installing random packages using the distro package manager (like yum, apt or brew), you declare the system configuration on the configuration.nix file. There, you can define the different packages you want to install widely on the system:

# ...
environment.systemPackages = with pkgs; [

On the other side, the nix.conf file defines the configuration for the nix installation. This file will be present in any nix installation, while the configuration.nix file will be available only when you install NixOS.

If you installed Nix as a "package manager" in an existing system, you can focus only on the nix.conf file. If your machine is based on NixOS, then you need to edit only the configuration.nix file. The nix.conf file will be auto-generated based on the nix.* options in your configuration file.