nh

Because the name "yet-another-nix-helper" was too long to type...

What Does it Do?

NH is a modern helper utility aims to consolidate and reimplement some of the commands from the NixOS ecosystem, including relevant 3rd party tools. Our goal is to provide a uniform interface with more features, and better ergonomics than existing commands.

Platform Specific Subcommands

• nh os - reimplements nixos-rebuild¹ with the addition of
  • build-tree displays.
  • diff of changes.
  • confirmation.
• nh home - reimplements home-manager.
• nh darwin - which reimplements darwin-rebuild.

Global Subcommands

• nh search - a super-fast package searching tool (powered by a ElasticSearch client).
• nh clean - a re-implementation of nix-collect-garbage that also collects gcroots.

Installation

The latest, tagged version will is available in Nixpkgs as NH stable. This repository provides the latest development version of NH, which you can get from the flake outputs.

nix shell nixpkgs#nh # stable
nix shell github:nix-community/nh # dev

NixOS

We provide a NixOS module that integrates nh clean as a service. To enable it, set the following configuration:

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

Nh supports both Flakes and classical NixOS configurations:

• For flakes, the command is nh os switch /path/to/flake
• For a classical configuration:
  • nh os switch -f '<nixpkgs/nixos>', or
  • nh os switch -f '<nixpkgs/nixos>' -- -I nixos-config=/path/to/configuration.nix if using a different location than the default.

You might want to check nh os --help for other values and the defaults from environment variables.

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
  };
}

Home-Manager

Home specialisations are read from ~/.local/share/home-manager/specialisation. The config would look like this:

{config, pkgs, ...}: {
  specialisation."foo".configuration = {
    xdg.dataFile."home-manager/specialisation".text = "foo";
    # ..rest of config
  };

  specialisation."bar".configuration = {
    xdg.dataFile."home-manager/specialisation".text = "bar";
    # ..rest of config
  };
}

Hacking

Contributions are always welcome. Just clone the repository and run nix develop. We also provide a .envrc for Direnv users.

Once your changes are complete, remember to run fix.sh to apply general formatter and linter rules that will be expected by the CI.

Lastly, update the changelog and open your pull request.

Attributions

NH would not be posible without that nh runs under the hood:

• Tree of builds with nix-output-monitor.
• Visualization of the upgrade diff with nvd.
• And of course, all the crates we depend on.

Status

---

1. nh os does not yet provide full feature parity with nixos-rebuild. While a large collection of subcommands have been implemented, you might be missing some features. Please visit #254 for a roadmap. ↩︎