nh

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

What does it do?

Nh is my own take at reimplementing some commands from the NixOS ecosystem. I aim to provide more feature and better ergonomics than the existing commands.

Nh has serveral subcommands, such as:

• os, which reimplements nixos-rebuild, with a tree of builds, diff and confirmation.
• home, which reimplements home-manager.
• search, a super-fast package searching tool (powered by a ElasticSearch client).
• clean, my own take at cleaning GC roots from a NixOS system.

This wouldn't be possible with the programs 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.

Installation

The latest stable version is available in Nixpkgs. This repository provides the latest development version of nh.

nix shell nixpkgs#nh # stable
nix shell github:viperML/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
  };
}

Status

Hacking

Just clone and nix develop. We also provide a .envrc for Direnv.