nixUnstable: error - disabled experimental feature

[Izorkin]

Error work command

nix edit -f ./default.nix mariadb
error: experimental Nix feature 'nix-command' is disabled

And hashes checksums incorrectly

nix build -f ./default.nix mariadb
hash mismatch in fixed-output derivation '/nix/store/g6a6y8ad45wjxcph32kbdlwqkjxach28-mariadb-10.3.20.tar.gz':
  wanted: sha256-QYGPLWhOBgFDtNgpPaRMfwnMZ21xlZQF+E5tyK/7xJI=
  got:    sha256-U4GPLWhOBgFDtNgpPaRMfwnMZ21xlZQF+E5tyK/7xJI=
cannot build derivation '/nix/store/6q15r7j59kapar7cyzmkjgmpnkvgmj2f-mariadb-server-10.3.20.drv': 1 dependencies couldn't be built
[0 built (1 failed), 0.0 MiB DL]
error: build of '/nix/store/6q15r7j59kapar7cyzmkjgmpnkvgmj2f-mariadb-server-10.3.20.drv' failed

• system: "x86_64-linux"
• host os: Linux 5.5.4-hardened, NixOS, 20.09.git.32bf68122c3 (Nightingale)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.4pre7250_94c93437
• channels(root): "nixos-20.09pre213593.6d881472ef7"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs

[Izorkin]

cc @edolstra

[edolstra]

Yes, this is expected. nix is now hidden behind an experimental feature flag. So you need to add experimental-features = nix-command to nix.conf or pass --experimental-features nix-command.

[Izorkin]

@edolstra thanks, worked with

  nix = {
    extraOptions = ''
      experimental-features = nix-command
    '';
  };

How to fix this sha256 checksumm

  wanted: sha256-QYGPLWhOBgFDtNgpPaRMfwnMZ21xlZQF+E5tyK/7xJI=
  got:    sha256-U4GPLWhOBgFDtNgpPaRMfwnMZ21xlZQF+E5tyK/7xJI=

[edolstra]

Hm, I can't reproduce the hash mismatch...

[Izorkin]

@edolstra in branch fc592a5 bad work. In d5bf8b2 correct work.

[Izorkin]

@edolstra revert this commit - dd7f6b0 - correct worked

[Izorkin]

@edolstra reproduced in virtual machine:

/etc/nixos/configuration.nix

{ config, pkgs, ... }:
{
  imports = [
    ./hardware-configuration.nix
  ];
  boot.loader.grub.enable = true;
  boot.loader.grub.version = 2;
  boot.loader.grub.device = "/dev/sda";
  networking.hostName = "nixos-test";
  networking.useDHCP = false;
  networking.interfaces.ens32.useDHCP = true;
  environment.systemPackages = with pkgs; [
    wget mc htop
  ];
  nix = {
    gc.automatic = false;
    optimise.automatic = true;
    readOnlyStore = true;
    useSandbox = true;
    package = pkgs.nixUnstable;
    extraOptions = ''
      experimental-features = nix-command
    '';
    nixPath = [
      "nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs"
      "nixos-config=/etc/nixos/configuration.nix"
      "/nix/var/nix/profiles/per-user/root/channels"
    ];
  };
  services.openssh.enable = true;
  networking.firewall.enable = false;
  users.users.test = {
    isNormalUser = true;
    extraGroups = [ "wheel" ];
  };
  system.stateVersion = "20.03";
}

sudo nix-channel --list
nixos https://nixos.org/channels/nixos-unstable-small

 nix-info -m
 - system: `"x86_64-linux"`
 - host os: `Linux 5.4.20, NixOS, 20.09pre213757.1e0222cd1f6 (Nightingale)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.4pre7250_94c93437`
 - channels(root): `"nixos-20.09pre213757.1e0222cd1f6"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs`

[mrkkrp]

Just FYI the same error is happening on activation of NixOS system after rebuild. The activation step fails:

> sudo nixos-rebuild switch
[sudo] password for mark: 
building Nix...
building the system configuration...
activating the configuration...
setting up /etc...
error: experimental Nix feature 'nix-command' is disabled
Activation script snippet 'nix' failed (1)
reloading user units for sddm...
reloading user units for mark...
setting up tmpfiles
warning: error(s) occurred while switching to the new configuration

I do not understand what in my configuration is using this experimental hidden feature. Probably nothing?

[edolstra]

It's probably

${nix}/bin/nix ping-store --no-net

in nixos/services/misc/nix-daemon.nix.

[mrkkrp]

@edolstra So what would be the proper fix for this? Replacing this use of the nix command or something else?

[AleXoundOS]

Experience the same problem with nixos-rebuild when using latest nix on nixos-20.03.

[stale]

I marked this as stale due to inactivity. → More info

[Mic92]

Should be no longer an issue in current maintained nixos versions.

[Izorkin]

In nix version 2.4pre20201205_a5d85d0 error not reproduced.

[jeff-hykin]

For anyone else getting here, it took me an embarrassingly long time to figure out that CLI command is supposed to literally look like this:

nix --extra-experimental-features nix-command --extra-experimental-features flakes flake lock A_FLAKE_URL

(when trying to do: nix flake lock A_FLAKE_URL)

Not this

nix --extra-experimental-features flake flake lock A_FLAKE_URL

Or this

nix --extra-experimental-features flakes flake lock A_FLAKE_URL

Or this

nix  flake lock A_FLAKE_URL --extra-experimental-features

Or this

nix --extra-experimental-features nix flake lock A_FLAKE_URL