nh

What does it do?

NH reimplements some basic nix commands. Adding functionality on top of the existing solutions, like nixos-rebuild, home-manager cli or nix itself.

As the main features:

• Tree of builds with nix-output-monitor
• Visualization of the upgrade diff with nvd
• Asking for confirmation before performing activation

Installation

Nixpkgs

nh is available in nixpkgs:

• https://search.nixos.org/packages?channel=unstable&query=nh
• Hydra status:
  • x86_64-linux: https://hydra.nixos.org/job/nixos/trunk-combined/nixpkgs.nh.x86_64-linux
  • aarch64-linux: https://hydra.nixos.org/job/nixos/trunk-combined/nixpkgs.nh.aarch64-linux

NixOS module

The NixOS module has some niceties, like an alternative to nix.gc.automatic which also cleans XDG profiles, result and direnv GC roots.

{ config, pkgs, ... }:
{
  programs.nh = {
    enable = true;
    clean.enable = true;
    clean.extraArgs = "--keep-since 4d --keep 3";
    flake = "/home/user/my-nixos-config";
  };
}

FLAKE environment variable

nh uses the FLAKE environment variable as the default flake to use for its operations. This can be configured by whichever method you want, or use the programs.nh.flake NixOS option.

Specialisations support

nh is capable of detecting which specialisation you are running, so it runs the proper activation script. To do so, you need to give nh some information of the spec that is currently running by writing its name to /etc/specialisation. The config would look like this:

{config, pkgs, ...}: {
  specialisation."foo".configuration = {
    environment.etc."specialisation".text = "foo";
    # ..rest of config
  };

  specialisation."bar".configuration = {
    environment.etc."specialisation".text = "bar";
    # ..rest of config
  };
}

Hacking

Just nix develop. We also provide an .envrc for direnv.