I’m very, very new to nix and nixOS both - I come from imperative workflows and very very rarely anything determinative, so this is all brand new to me.

As an example of the kind of thing I don’t understand how to do, let’s take an example repo I’ve been bouncing off: https://github.com/GideonWolfe/Chameleon

On a “normal” system, I can get pip and python ready, and then make install and I’m off to the races.

With NixOS, I’ve got as far as adding python3 and gnumake to my configuration.nix packages. (I have also discovered that putting python in my system packages was the wrong move, so some advice on how better to go about this would be cool too.)

I can’t for the life of me wrap my head around what I’m supposed to do, and so many people online are using flakes but I’m on stable 23.11 (and quite daunted by flakes) so I’d prefer if this was from that POV.

Can anyone speak to any of these points? I’ve tried reading the docs but it’s very confusing for some reason.

  • onlinepersonaEnglish
    121·
    6 months ago

    Here are the basic steps though:

    • package the target in a derivation aka a recipe to package the thing you like
    • test it in a nix-shell or add it straight to your configuration.nix

    I know it sounds a lot like , but a few pointers:

    Derivation basics: This wiki page is the one that helped me understand the basics of derivations. It explains how to package stuff without extra tooling. stdenv.mkDerivation from nixpkgs adds a bunch of stuff, but the wiki linked doesn’t explain it (yet?). You might find more information elsewhere.

    There’s documentation for stdenv.mkDerivation and I apologize in advance for putting this evil upon you, but right now I don’t have any other useful bookmarks. I learned it the hard way, but if you can contribute to the https://nixlang.wiki with what you learned, you could make it easier for the next person.

    As for nix-shell, once you’ve written your default.nix, you can wrap it in a shell.nix and execute nix-shell in the same directory.

    default.nix

    { pkgs ? import <nixpkgs> {} }:
pkgs.stdenv.mkDerivation {
  pname = "chameleon";
  version = "0.0.1"; # Update this to the real version of the package
  buildInputs = with pkgs; [ gnumake ]; # Add more necessary inputs here

  # While testing, your default.nix can reside in the checked out git repo
  src = ./.;
  # You can of course also start out like this straight away, up to you
  # Once testing is done, you can point this to a git repo pulled by nix
  # src = pkgs.fetchFromGitHub {
  #   owner = "GideonWolfe";
  #   repo = "Chameleon";
  #   rev = "SOME GIT REVISION";
  #   hash = "";  # Start with an empty string and let nix complain with the real one, the use it
  #  };

  # There's a chance an install phase isn't necessary, but this is a skeleton
  # The contents are run in bash
  installPhase = ''
   runHook preInstall
   
   # Do non-standard installation stuff
   # See https://nixos.org/manual/nixpkgs/stable/#ssec-install-phase
   # for what is done by default

   runHook postInstall
  '';
}

    shell.nix

    { pkgs ? import <nixpkgs> {} }:
let
  my-package = (import ./default.nix) { pkgs = pkgs; };
in
pkgs.mkShell {
  inputsFrom = [ my-package ];
}

    Then you can run nix-shell and see if your expected binary is in PATH. Once that is confirmed, you can add your package to your configuration.nix

    { config, pkgs, ... }:

{
  # The rest of your configuration.nix

  environment.systemPackages = with pkgs; [
    # Import and call your derivation
    ((import /path/to/your/default.nix) { inherit pkgs; })
  ];
}

    Hopefully that helped a little.

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    • apotheotic (she/her)@beehaw.orgOPEnglish
      3·
      6 months ago

      Thank you deeply for such a thorough answer! If I make any discoveries that aren’t documented I will definitely try to contribute to the wiki.

    • apotheotic (she/her)@beehaw.orgOPEnglish
      1·
      6 months ago

      Random question - my current setup is all done through configuration.nix. Do you think it would be wise at this stage to pivot to learning about flakes and using them instead (as the other comments have suggested, flakes appear to be the way to go), prior to introducing more complexity on my system (installing chameleon, etc)?

      • onlinepersonaEnglish
        1·
        6 months ago

        I’m sorry, but I don’t use flakes, therefore my opinion on the topic should be taken with a grain of salt. To me they are unstable, the documentation worse than standard nix (which is bad enough IMO), and there a few pitfalls I’ve seen here and there that dissuade me from using it. However, there are people who swear by it 🤷

        What I would recommend is to just try it out and see for yourself, then make the call. Maybe not straight away with your entire system, but you could try out some flakes project or something.
        If you do want to start out with your system, then make a backup of /etc/nixos/, and write down somewhere which generation you’re currently on, so that you can always reboot and jump into a backup configuration.

        Whatever you learn with standard nix won’t be lost when/if you decide to use flakes.

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