anchor.diff:      # Menu configuration
       #
   
  +    # Search using a "marker file"
  +    search --set=root --file /EFI/nixos-installer-image
  +
       insmod gfxterm
       insmod png
       set gfxpayload=keep
  
positive.code:     ${lib.optionalString (refindBinary != null) ''
      # GRUB apparently cannot do "chainloader" operations on "CD".
      if [ "\$root" != "cd0" ]; then
        menuentry 'rEFInd' --class refind {
          # \$root defaults to the drive the EFI is found on.
          chainloader (\$root)/EFI/boot/${refindBinary}
        }
      fi
  
negative.code:   } ''
      mkdir -p $out/EFI/boot/
  
      # Add a marker so GRUB can find the filesystem.
      touch $out/EFI/nixos-installer-image
  
      # ALWAYS required modules.
      MODULES="fat iso9660 part_gpt part_msdos \
               normal boot linux configfile loopback chain halt \
  