Hi, I'm using import-from-derivation to obtain my nixpkgs copy (to be able to inject v

`colmena build` fails when `meta.nixpkgs = import-from-derivation ...` about colmena HOT 2 CLOSED

bjornfor commented on June 15, 2024 1

`colmena build` fails when `meta.nixpkgs = import-from-derivation ...`

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Comments (2)

zhaofengli commented on June 15, 2024 1

First of all, I think this specific usecase can be done without IFD:

let
  nixpkgs = builtins.fetchGit {
    url = "https://github.com/NixOS/nixpkgs.git";
    ref = "refs/heads/release-21.05";
    rev = "c4cbbed186cc00066fd1998b5d915fe37f197135";
  };
in {
  meta = {
    nixpkgs = import nixpkgs {};
  };

  defaults = {
    system.nixos.version = "21.05-${nixpkgs.shortRev}";
  };

  host1 =
    { pkgs, ... }:
    {
      fileSystems."/".device = "/dev/sda";
      boot.loader.grub.devices = [ "/dev/sda" ];
    };
}

IFD doesn't work in this case because Colmena is using nix-instantiate --eval in read-only mode. A simpler way to reproduce is:

# simple-ifd.nix
let
  nixpkgs = builtins.fetchGit {
    url = "https://github.com/NixOS/nixpkgs.git";
    ref = "refs/heads/release-21.05";
    rev = "c4cbbed186cc00066fd1998b5d915fe37f197135";
  };
  pkgs = import nixpkgs {};
  drv = pkgs.writeText "some.nix" "123";
in import drv

This fails:

nix-instantiate --eval --json simple-ifd.nix

However, this succeeds:

nix-instantiate --eval --json --read-write-mode simple-ifd.nix

What do other deployment tools do? From a cursory look, NixOps always appends --read-write-mode by default (which came from NixOS/nixops#279), and morph doesn't do that.

I currently can't think of any cases where we would not want store paths to be built when we do an --eval, so let's add this so IFD works. For colmena eval, this can also make things less confusing because currently store paths returned in the default eval mode are not valid.

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bjornfor commented on June 15, 2024

Thank you!

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