diff --git a/frontend/grub-mkrescue-sed.sh b/frontend/grub-mkrescue-sed.sh
index dcd9d696..1a485cd8 100755
--- a/frontend/grub-mkrescue-sed.sh
+++ b/frontend/grub-mkrescue-sed.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-# Copyright (C) 2015 - 2019
+# Copyright (C) 2015 - 2022
 # Thomas Schmitt <scdbackup@gmx.net>, libburnia-project.org
 # Provided under BSD license: Use, modify, and distribute as you like.
 
@@ -117,9 +117,9 @@ fi
 #  command line.)
 # Each argument must be a single word. No whitespace. No quotation marks.
 
-# "yes" overwrites the MBR partition table area in the EFI boot image by zeros.
-# Some EFI implementations get stuck when seeing in the EFI partition a
-# partition table entry which begins at LBA 0.
+# "yes" in MKRESCUE_SED_IN_EFI_NO_PT overwrites the MBR partition table area
+# in the EFI boot image by zeros. Some EFI implementations get stuck when
+# seeing in the EFI partition a partition table entry which begins at LBA 0.
 # "extra" not only zeros the partition table but also the MBR signature.
 efi_zero_inner_pt=no
 if test -n "$MKRESCUE_SED_IN_EFI_NO_PT"
@@ -127,6 +127,24 @@ then
   efi_zero_inner_pt="$MKRESCUE_SED_IN_EFI_NO_PT"
 fi
 
+# "yes" in MKRESCUE_SED_UNPACK_EFI_TO_ISO causes the file tree from the FAT
+# image efi.img to be unpacked by mcopy to a directory in /tmp which then
+# gets mapped into the root directory of the emerging ISO 9660 filesystem.
+# This enables a way of installing the result image onto a USB stick with
+# FAT filesystem by simply copying its full file tree from ISO to FAT.
+# Whether the payload files of the ISO will be able to work from FAT depends
+# on their expectation towards file names and attributes.
+# WARNING: Make sure that the files in efi.img do not collide with your
+#          payload files or with files added to the ISO by GRUB. Before using
+#          MKRESCUE_SED_UNPACK_EFI_TO_ISO, make a vanilla grub-mkrescue ISO
+#          with your payload, mount it and then its /efi.img file, then use
+#          program "find" on the mount point of efi.img to see all its files.
+#          Compare this with the output of "find" on the ISO mount point.
+efi_unpack_to_iso=no
+if test -n "$MKRESCUE_SED_UNPACK_EFI_TO_ISO"
+then
+  efi_unpack_to_iso="$MKRESCUE_SED_UNPACK_EFI_TO_ISO"
+fi
 
 #
 #                               Do the work 
@@ -190,10 +208,11 @@ done
 if test x"$debug" = xextra
 then
   # Show files on disk
-  find "$dir"
+  find "$dir" 2>&1
+  echo 2>&1
 fi
 
-if test "$efi_zero_inner_pt" = yes -o "$efi_zero_inner_pt" = extra
+if test x"$efi_zero_inner_pt" = xyes -o x"$efi_zero_inner_pt" = xextra
 then
   did_dd=0
   if test -e "$dir"/efi.img
@@ -222,6 +241,41 @@ then
   fi
 fi
 
+efi_temp_tree=
+if test x"$efi_unpack_to_iso" = xyes
+then
+  if test -e "$dir"/efi.img
+  then
+    temp_tree=/tmp/grub-mkrescue-sed-et."$$"
+    # The mcopy command is the inverse of what grub-mkrescue does to pack it up
+    if mcopy -s -i "$dir"/efi.img ::/ "$temp_tree"
+    then
+      efi_temp_tree="$temp_tree"
+      if test x"$debug" = xyes -o x"$debug" = xextra
+      then
+        echo "Temporarily extracted $dir/efi.img to $temp_tree" >&2
+        echo >&2
+        if test x"$debug" = xextra
+        then
+          # Show extracted files
+          find "$temp_tree" >&2
+          echo >&2
+        fi
+      fi
+    elif test -e "$temp_tree"
+    then
+      rm -r "$temp_tree"
+    fi
+    if test -z "$efi_temp_tree"
+    then
+      echo >&2
+      echo "$0 : NOTE : Could not extract efi.img to $temp_tree" >&2
+      echo "$0 : NOTE : Thus cannot obey MKRESCUE_SED_UNPACK_EFI_TO_ISO." >&2
+      echo >&2
+    fi
+  fi
+fi
+
 efi_tmp_name=
 if test x"$mode" = xmjg \
      -o x"$mode" = xmbr_only \
@@ -229,10 +283,15 @@ if test x"$mode" = xmjg \
      -o x"$mode" = xmbr_hfs
 then
   # Move EFI partition image file out of the "$dir" tree, i.e. out of the ISO
-  efi_tmp_name=grub-mkrescue-sed-efi-img.$$
+  efi_tmp_name=grub-mkrescue-sed-ei.$$
   if test -e "$dir"/efi.img
   then
     mv "$dir"/efi.img /tmp/$efi_tmp_name
+    if test x"$debug" = xyes -o x"$debug" = xextra
+    then
+      echo "Temporarily moved $dir/efi.img to /tmp/$efi_tmp_name" >&2
+      echo >&2
+    fi
   elif test -e /tmp/$efi_tmp_name
   then
     rm /tmp/$efi_tmp_name
@@ -322,6 +381,27 @@ else
   exit 1
 fi
 
+if echo "$efi_temp_tree" | grep '^/tmp/' >/dev/null
+then
+  # Does the xorriso run end in native command mode ?
+  separator_seen=0
+  for i in "$@"
+  do
+    if test x"$i" = x--
+    then
+      separator_seen=1
+    fi
+  done
+  if test "$separator_seen" = 1
+  then
+    # Native mode possible: Enable it for sure and then use -map
+    x=" $x -- -map $efi_temp_tree /"
+  else
+    # Hopefully nobody finds a way to leave mkisofs emulation without "--" arg
+    x=" $x -graft-points /=$efi_temp_tree"
+  fi
+fi
+
 if test x"$debug" = xyes -o x"$debug" = xextra
 then
   echo "+ converted xorriso arguments:" >&2
@@ -349,5 +429,11 @@ then
    mv /tmp/$efi_tmp_name "$dir"/efi.img
 fi
 
+# Remove possible extracted EFI partition tree
+if echo "$efi_temp_tree" | grep '^/tmp/' >/dev/null
+then
+  rm -r "$efi_temp_tree"
+fi
+
 exit $ret
 
diff --git a/frontend/grub-mkrescue-sed.sh.sig b/frontend/grub-mkrescue-sed.sh.sig
new file mode 100644
index 00000000..5efa530e
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