nix/module/common/Nix.nix

{ pkgs, ... }: {
	environment.variables = {
		# Allow running of proprietary software.
		NIXPKGS_ALLOW_UNFREE = "1";

		# I use this env variable to get currently running architecture.
		NIX_CURRENT_SYSTEM = "${pkgs.stdenv.system}";
	};

	# Allow installation of proprietary software.
	nixpkgs.config.allowUnfree = true;

	# Deduplicate store automatically. Slows down switches a bit, but saves space.
	nix.settings.auto-optimise-store = true;

	# Extra configuration line-by-line:
	# 1. Allow use of flakes.
	# 2. When running GC, keep .drv files.
	# 3. When running GC, keep build dependencies.
	# 4. Run GC automatically when there's a 50 GB or less free space.
	nix.extraOptions = ''
		experimental-features = nix-command flakes
		keep-derivations = true
		keep-outputs = true
		min-free = ${toString (50 * 1000 * 1000 * 1000)}
	'';

	# NOTE: Currently I run GC completely, but this setting (put above near min-free)
	# can stop GC when you hit 101 GB of free space available.
	# max-free = ${toString 101 * 1024 * 1024 * 1024}

	# NOTE: Enable this if you want to run GC on schedule. I instead use `min-free`.
	# nix.gc = {
	# 	automatic  = true;
	# 	dates      = "weekly";
	# 	options    = "--delete-older-than 30d";
	# 	persistent = true;
	# };
}