anchor.diff:    bootScript = pkgs.writeScript "bootscript.sh" ''
       #!${pkgs.stdenv.shell} -eux
   
  -    echo "attempting to fetch configuration from user-data..."
  +    echo "attempting to fetch configuration from EC2 user data..."
   
       export PATH=${config.nix.package}/bin:${pkgs.wget}/bin:${pkgs.systemd}/bin:${pkgs.gnugrep}/bin:${pkgs.gnused}/bin:${config.system.build.nixos-rebuild}/bin:$PATH
       export NIX_PATH=/nix/var/nix/profiles/per-user/root/channels/nixos:nixos-config=/etc/nixos/configuration.nix:/nix/var/nix/profiles/per-user/root/channels
  
positive.code:     wget -q --wait=1 --tries=0 --retry-connrefused -O - http://169.254.169.254/2011-01-01/user-data > "$userData"
  
      if [[ $? -eq 0 ]]; then
        echo "user-data fetched"
        # If the user-data looks like it could be a nix expression,
        # copy it over. Also, look for a magic three-hash comment and set
        # that as the channel.
  
negative.code:           nix-channel --update
          fi
  
          echo "setting configuration from EC2 user data"
          cp "$userData" /etc/nixos/configuration.nix
        else
          echo "user data does not appear to be a Nix expression; ignoring"
          exit
        fi
      else
        echo "failed to fetch user data"
        exit
      fi
  
      nixos-rebuild switch
    '';
  