Snippet to include into your nixos configuration to run a nsncd (non-caching NSS daemon, written in Rust)

nsncd.nix

{ pkgs, lib, ... }:

let
  nsncdPackage = pkgs.rustPlatform.buildRustPackage rec {
    pname = "nsncd";
    version = "unstable-2021-10-13";

    src = pkgs.fetchFromGitHub {
      owner = "flokli";
      repo = "nsncd";
      rev = "c9f7ba1cfe482200a8f722b5f7c3e9c5042fe1a8";
      hash = "sha256-n6nDqNVBQQYmYsJ/a8lRxwKRR6kgpJhko5KrODLHFT8=";
    };

    cargoSha256 = "sha256-lBK5Q/+FAvxgTQEudbYOGKJGtw0Lx5UJgUP8GTjAqAs=";
    
    # dumps tons of logs into the systemd journal in debug mode, drop line if running in a prod-like scenario
    buildType = "debug";
  };

in
{
  systemd.services.nscd.serviceConfig.ExecStart = lib.mkForce "${nsncdPackage}/bin/nsncd";
  systemd.services.nscd.serviceConfig.Type = lib.mkForce "notify";
  systemd.services.nscd.serviceConfig.ExecReload = lib.mkForce [ ];
}