Hi! I'm finally migrating my 6 years old nixos config to Flakes! It's mostly going well but I need some help. I used to have an overlay that added nixpkgs-unstable to the nixpkgs.unstable attribute (using fetchTarball to get it). Now, I want to use a flake input instead, and I used an inline module with an overlay to have it exposed in the same place again. I'm trying to make my existing modules compatible with the Flake, so I don't have to go in and change them all.

This all seems to work, except that Nix is refusing to evaluate Unfree packages from Unstable now. It appears as though the nixpkgs.config does not apply to the unstable input the way it used to. So my question is: How do I get this second nixpkgs input to adhere to the same config as my primary one? And by "primary" I guess I mean the one used to make the lib.nixosSystem call.

In reply to @avaq:matrix.org
Oh? And then there's no need to mention the system architecture? :o

In reply to @avaq:matrix.org
I'm also curious about how import inputs.x works. I thought input.x is an attribute set referring to the outputs of the flake you've imported. But it's also an import path referring to the source of what you've imported?!

In reply to @petrichor:envs.net
flakes are attribute sets with _type = "flake", but when coerced to a string (builtins.toString) or a path (builtins.toPath) they resolve to the flake's store path

In reply to @petrichor:envs.net
i think your overlay could look like final: prev: { unstable = import inputs.unstable { inherit (prev) system config; } but you might get away with omitting system

In reply to @janik0:matrix.org
of course, how else would I get people to do free qa :D

In reply to @ryoschin:matrix.org
When using flakes to manage my system, and having `nixos-unstable` and `home-manager` as inputs, I have to call `sudo nixos-rebuild switch --flake some/path`. Now, that command sometimes downloads around 300 MB of data before actually doing the build (around 150 MB for unstable I suppose, and 148 MB for home-manager). Is it possible to avoid having to wait for that every time? I suppose it might do the downloading when I run `sudo nix-collect-garbage -d` and reboot. (Copied from NixOs, this room might be more suitable for this question)

you can try with --offline then it will try to run any nix * command with the local data from nix cache also stops nix shell and nix run from trying to refresh the remote nix version. Alternatively you can do:

  nix.registry = {
    nixpkgs.flake = inputs.nixpkgs;
  };

that pins any nix * command to the same flake.lock version (similar to what channels or npins or nivs would do for nix-* commands)