Pad runtime to multiple of 512 bytes

src/build-runtime.sh.in

@@ -66,9 +66,20 @@ HEXOFFSET=$(objdump -h runtime | grep .upd_info | awk '{print $6}')
 HEXLENGTH=$(objdump -h runtime | grep .upd_info | awk '{print $3}')
 dd bs=1 if=runtime skip=$(($(echo 0x$HEXOFFSET)+0)) count=$(($(echo 0x$HEXLENGTH)+0)) | xxd
 
+APPIMAGEOFFSET=$(./runtime --appimage-offset)
+
 # Insert AppImage magic bytes
 printf '\x41\x49\x02' | dd of=runtime bs=1 seek=8 count=3 conv=notrunc
 
+# Pad runtime to multiple of 512bytes
+dd if=/dev/null of=runtime bs=1 count=1 seek=$APPIMAGEOFFSET
+
+# Add boot signature to runtime, this way fdisk recognize the appimage as a partitioned disk image
+printf '\x55\xaa' | dd of=runtime bs=1 seek=510 count=2 conv=notrunc
+
+# Add partition entry to runtime, this way gnome-disk-image-mounter can open it.
+printf "0x%08x" $((APPIMAGEOFFSET / 512 )) | xxd -r | tac -rs. | dd of=runtime bs=1 seek=454 count=4 conv=notrunc
+
 # Convert runtime into a data object that can be embedded into appimagetool
 ld -r -b binary -o data.o runtime
 

src/runtime.c

@@ -289,7 +289,9 @@ main (int argc, char *argv[])
     sprintf(argv0_path, argv[0]);
 
     fs_offset = get_elf_size(appimage_path);
-
+    /*It's better to keep filesystems aligned at 512bytes intervals, like sectors on a real partitioned disk*/
+    fs_offset = ((fs_offset-1)|511)+1;
+
     arg=getArg(argc,argv,'-');
 
     /* Print the help and then exit */