let fetch = { file, sha256 }:
    let
      nixFetchurl = import <nix/fetchurl.nix>;
      args = {
        url = "file://${builtins.toString ./.}/${file}";
        inherit sha256;
        executable = true;
      };
    in if (builtins.functionArgs nixFetchurl) ? executable
      then nixFetchurl args
      else derivation {
        name = file;
        builder = "/bin/sh";

        system = builtins.currentSystem;

        args = [ "-c" "echo $message; exit 1" ];

        message = ''
          Sorry, this version of nix cannot download all of the bootstrap tools.
          Please download ${args.url}, make it executable, add it to the store
          with `nix-store --add', and try again.
        '';

        outputHashAlgo = "sha256";

        outputHash = args.sha256;

        outputHashMode = "recursive";

        preferLocalBuild = true;
      };
in {
  sh = fetch {
    file = "sh";
    sha256 = "1kv3gc8h209rjc5i0rzzc4pjxq23kzq25iff89in05c9vl20mn4n";
  };

  bzip2 = fetch {
    file = "bzip2";
    sha256 = "090jrj099wl33q0iq092iljilam39pv8acli59m2af0fa9z0d9f0";
  };

  mkdir = fetch {
    file = "mkdir";
    sha256 = "01s8myfvi559dsxvbanxw71vxzjv49k4gi1qh0ak6l0qx0xq602b";
  };

  cpio = fetch {
    file = "cpio";
    sha256 = "07snc8l0mn84w2xrvdmc5yfpmlbrvl2bar8wipbpvm43nzz2qbzs";
  };

  ln = fetch {
    file = "ln";
    sha256 = "0m9fz02bashpfgwfkxmrp4wa8a5r3il52bclvf6z36vsam0vx56d";
  };

  curl = fetch {
    file = "curl.bz2";
    sha256 = "19yqdjqi31zlnqn8ss2ml60iq2a1vrwfw6dmvjqp6qbxmh7yb8n8";
  };

  bootstrapTools = {
    url = "http://tarballs.nixos.org/stdenv-linux/armv5tel/r18744/bootstrap-tools.cpio.bz2";
    sha256 = "1rn4n5kilqmv62dfjfcscbsm0w329k3gyb2v9155fsi1sl2cfzcb";
  };
}