Is there a default declarative Nix configuration for non-NixOS systems?

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1

Is there a default declarative Nix configuration similar to .config/home-manager/home.nix that can install Nix packages into a profile? I’m running Nix in Ubuntu Server, not NixOS.

2

You can use buildEnv to do things like that: Nixpkgs 23.05 manual | Nix & NixOS

home-manager does a lot of additional heavy lifting for systemd user services and configuration symlinks that aren’t trivial with this approach.

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3

What is the equivalent of nix-env -iA nixpkgs.myPackages and nix-env -f. -iA myPackages using the new experimental nix commands?

4

That doesn’t exist. You’d probably do something with a flake.nix:

{
  inputs = {
    # Grab a static nixpkgs or the one from your registry
  };

  outputs = {nixpkgs, ...}: let
    system = "x86_64-linux";
    pkgs = nixpkgs.legacyPackages.${system};
  in {
    packages.${system}.default = pkgs.buildEnv {
      name = "my-packages";
      paths = with pkgs; [
        aspell
        bc
        coreutils
        gdb
        ffmpeg
        nixUnstable
        emscripten
        jq
        nox
        silver-searcher
      ];
    };
  };
}

Then install with nix profile install .#

YMMV, this is more pseudocode than anything else, I haven’t tested it at all.

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5

How does nix profile install .# know to “install” the flake?

6

nix profile install .# will look at the flake outputs, and look for an outputs.packages.${system}.default. .# in this case tells nix what to install, specifically an output of the flake in the current directory (.), and since we omit the output it will install the default one. See this doc for details.

If the default output exists, and is a derivation, it will add that derivation to the profile, which basically just means that nix will add certain symlinks from those packages to your nix profile directory, which in turn should be referred to in $PATH and the like so that you can run the binaries in question.

buildEnv in this case just collects all packages in its paths into such a set of symlinks, which are then recursively installed into your profile.