{ pkgs, ... }: {

  nix = {
    systemFeatures = [ "nixos-test" "benchmark" "big-parallel" "kvm" ];

    autoOptimiseStore = true;

    gc.automatic = true;

    optimise.automatic = true;

    useSandbox = true;

    allowedUsers = [ "@wheel" ];

    trustedUsers = [ "root" "@wheel" ];

    extraOptions = ''
      min-free = 536870912
      keep-outputs = true
      keep-derivations = true
      fallback = true
    '';
  };

  environment = {
    systemPackages = with pkgs; [ nix-index nixfmt nixpkgs-fmt ];

    shellAliases = {
      # nix
      n = "nix";
      np = "n profile";
      ni = "np install";
      nr = "np remove";
      ns = "n search --no-update-lock-file";
      nf = "n flake";
      nepl = "n repl '<nixpkgs>'";
      srch = "ns nixos";
      orch = "ns override";
      nrb = ifSudo "sudo nixos-rebuild";
      mn = ''
        manix "" | grep '^# ' | sed 's/^# \(.*\) (.*/\1/;s/ (.*//;s/^# //' | sk --preview="manix '{}'" | xargs manix
      '';

      # fix nixos-option
      nixos-option = "nixos-option -I nixpkgs=${self}/lib/compat";
    };
  };
}