Hi, i wrote: > > zeroize 512-byte block 1 of the > > Debian Live ISO and then try to boot it from USB stick
Michel Bouissou wrote: > I made it (with latest debian-gnome 9.3 live),i Now we have no surplus GPT any more. The EFI system partition is only marked by the MBR partition 2 (and by the El Torito catalog which should be ignored when found on USB stick). > and tested it OK on *another* machine. > But on the machine where the problem is, it does *NOT* boot. Normally i would now again exclude the theory that the partitions inside the ISO are to blame. (We still have to explain why the GRUB installations on hard-disk-like partitioned USB sticks failed too.) > It does display the key brand/model (instead of "Windows boot manager") But this slight change in firmware behavior could be significant. Under the theory that it's the partition layout and not the EFI partition image content or its way to hop on the ISO, there remains the nested partition situation as main suspect: $ /sbin/fdisk -l debian-live-9.3.0-amd64-xfce.iso ... Device Boot Start End Sectors Size Id Type debian-live-9.3.0-amd64-xfce.iso1 * 0 3803903 3803904 1.8G 0 Empty debian-live-9.3.0-amd64-xfce.iso2 1548 2379 832 416K ef EFI The block range of partition 2 is inside partition 1. Normally the type 0 ("Empty") of partition 1 is enough to let firmwares tolerate this. Partition 1 is not needed for the boot process. It just protects the ISO from partition editors and provides a mountable partition to operating systems. So the next experiment would be to remove it, i.e. zeroize its slot in the MBR. One can do it in the ISO file img=debian-live-9.3.0-amd64-xfce.iso or directly on the USB stick where it was copied img=/dev/sdc Either by: /sbin/fdisk "$img" <<+ d 1 w + Or by: dd if=/dev/zero bs=1 seek=446 count=16 conv=notrunc of="$img" The result should then be $ /sbin/fdisk -l "$img" ... Device Boot Start End Sectors Size Id Type debian-live-9.3.0-amd64-xfce.iso2 1548 2379 832 416K ef EFI Have a nice day :) Thomas _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel