anchor.diff:  
     efiImg = pkgs.runCommand "efi-image_eltorito" { buildInputs = [ pkgs.mtools pkgs.libfaketime ]; }
       # Be careful about determinism: du --apparent-size,
  -    #   dates (cp -p, touch, mcopy -m, faketime for label), IDs (mkfs.vfat -i)
  +    #   dates (cp -p, touch, mcopy -m, faketime for label), IDs (mkfs.vfat -i),
  +    #   mcopy's write order (-s uses `readdir` order)
       ''
  +      # Prepare the ./EFI and ./boot directories
         mkdir ./contents && cd ./contents
         cp -rp "${efiDir}"/EFI .
         mkdir ./boot
  
positive.code:         "${config.system.build.initialRamdisk}/${config.system.boot.loader.initrdFile}" ./boot/
        touch --date=@0 ./EFI ./boot
  
        usage_size=$(du -sb --apparent-size . | tr -cd '[:digit:]')
        # Make the image 110% as big as the files need to make up for FAT overhead
        image_size=$(( ($usage_size * 110) / 100 ))
  
negative.code:       echo "Usage size: $usage_size"
        echo "Image size: $image_size"
        truncate --size=$image_size "$out"
  
        # Make the filesystem
        ${pkgs.libfaketime}/bin/faketime "2000-01-01 00:00:00" ${pkgs.dosfstools}/sbin/mkfs.vfat -i 12345678 -n EFIBOOT "$out"
  
        # Copy the files
        # Note: we can't use mcopy's recursive copying as it uses `readdir` order.
        # So just copy file-after-file
        find ./EFI ./boot -type f -print0 | sort -z | \
          xargs -0I '{}' mcopy -pvm -i "$out" '{}' ::
  
        # Verify the FAT partition.
        ${pkgs.dosfstools}/sbin/fsck.vfat -vn "$out"
      ''; # */
  