How to prevent flake from downloading registry at every flake command?

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1

it constantly annoys me it taking 3-5 seconds downloading the flake registry when it is irrelevant

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2

I don’t know if there’s a way to decrease the frequency in which the registry is checked for updates.
But something I do (and you may find even better) is pinning the registry to use the same version of nixpkgs as your system.

{
  nix.registry.nixpkgs.flake = inputs.nixpkgs; # For flake commands
  nix.nixPath = [ "nixpkgs=${inputs.nixpkgs}" ]; # For legacy commands
}

I’m not sure if there’s a way to get overlays working with this, that would be fun.

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3

In addition to what @lelgenio did, you can also do this to avoid downloading the flake registry altogether

  inputs.flake-registry = {
    url = "github:nixos/flake-registry";
    flake = false;
  };

  nix.settings.flake-registry = "${inputs.flake-registry}/flake-registry.json";
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4

I’m setting

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

which, if I understand correctly, takes the default pkgs instantiation of nixpkgs after applying overlays. So that should work?

5

I don’t think that works, I tried using this:

nix.registry.nixpkgs.to = {
  type = "path";
  path = pkgs.path;
};
nix.nixPath = [ "nixpkgs=${pkgs.path}" ];

And neither nix run (uses registry) nor comma (uses nixPath) could find packages from overlays.

6

Ah, interesting, but you got the normal nixpkgs then?
Could this have to do with lazyness? I think there are some gurus that understand in-depth nixpkgs instantiation here?

So then maybe an explicit instance could help? Something like

nix.nixPath [ "nixpkgs=${import inputs.nixpkgs { inherit (pkgs) system config; overlays = [ ... ]; }}" ];

But I guess this is kind of ugly (a new nixpkgs instance), so there must be a better way?