question: using useGlobalPkgs with standalone installation

[ezracelli]

Is there a way to set home-manager.useGlobalPkgs (or achieve the same goal — using the global pkgs) using the standalone installation? I am on a NixOS system, if it makes a difference. Thanks!

[rycee]

If your NixOS configuration includes overlays and such then it would be a bit tricky to make use of that in your HM configuration. In principle it would probably work but you would need to evaluate your NixOS configuration and assign its final pkgs into HM's _module.args.pkgs.

If your NixOS configuration simply uses a plain nixpkgs clone then you can simply make sure <nixpkgs> points to that clone. I do this in my HM configuration by having

nix.nixPath = [ "nixpkgs=/home/rycee/devel/nixpkgs-22.11" ];

in my configuration. Then home-manager switch etc. will pick it up automatically.

[ppenguin]

That assignment @rycee talks about I have implemented like so:

In system overlays (this overlays/default.nix is simply listed as a module at system instantiation:

{ inputs, pkgs, unstable, ... }:

{
    nixpkgs.overlays = [
        (import ./some-overlay.nix)
    ];

    # this *adds* unstable to the available args for all modules
    _module.args.unstable = import inputs.nixpkgs-unstable { inherit (pkgs) system config; };

    nix.nixPath = [ "nixpkgs=${pkgs.path}" "unstable=${unstable.path}" ];
}

and for the HM generation I'm doing something like (simplified):

let
  inherit (systemConfigs."${hostname}") pkgs config;
in
{
  ...
  inputs.home-manager.lib.homeManagerConfiguration {
      inherit pkgs;
      ...
  };
}

where systemConfigs is passed to this function (that generates the user's HM flake output) like this:

systemConfigs = inputs.self.nixosConfigurations // inputs.self.darwinConfigurations;

(it seems I need to do this myself, since the documented standard argument osConfig (if I remember correctly) didn't seem to work in standalone mode)

[ezracelli]

Thanks for the quick responses! I think I was a bit confused, and I still am (Nix is so complicated!) — thanks for bearing with me.

• I am not using flakes; I have an /etc/nixos/configuration.nix and an ~/.config/nixpkgs/home.nix, that's it
• home-manager was installed using the standalone method, i.e. nix-shell '<home-manager>' -A install
• I have not customized my NIX_PATH at all, so its value is the default:

  [
    "nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos"
    "nixos-config=/etc/nixos/configuration.nix"
    "/nix/var/nix/profiles/per-user/root/channels"
  ]

I think the above means that home-manager is actually already using the system nixpkgs. Indeed, the following two zsh store paths match:

# the zsh defined in `configuration.nix`:
# 
# ```
# programs.zsh.enable = true;
# users.defaultUserShell = pkgs.zsh;
# ```
$ realpath /run/current-system/sw/bin/zsh
/nix/store/6fm0farw5fgl8w04nxl3241s1kgwijjq-zsh-5.9/bin/zsh

# the zsh defined in `home.nix`:
#
# ```
# programs.zsh.enable = true;
# ```
$ realpath ~/.nix-profile/bin/zsh
/nix/store/6fm0farw5fgl8w04nxl3241s1kgwijjq-zsh-5.9/bin/zsh

---

Specifically what I was trying to do was use a 1Password wrapper in my git config (managed by home-manager). However, unlike zsh above, the store paths differ:

# the 1Password defined in `configuration.nix`:
# 
# ```
# programs._1password-gui.enable = true;
# ```
$ realpath /run/current-system/sw/bin/1password
/nix/store/sh9rir830bxdz24a094ny49v9ffw9h93-1password-8.9.8/bin/1password

# the 1Password defined in `home.nix`:
# 
# ```
# programs.git.extraConfig.gpg.ssh.program = "${pkgs._1password-gui}/share/1password/op-ssh-sign";
# ```
$ cat ~/.config/git/config | grep 1password
    program = "/nix/store/xz00fxs1kh5w5m51dpqbllx7d8v9vcs7-1password-8.9.8/share/1password/op-ssh-sign"
#   expected: "/nix/store/sh9rir830bxdz24a094ny49v9ffw9h93-1password-8.9.8/share/1password/op-ssh-sign"

The specific question I'm trying to answer is: Why do these store paths differ? and is there a way that they can … not?