Hi, another experiment proposal for Dominik 'Rathann' Mierzejewski: Zeroize the GPT of a copy of boot-grub2-f36.iso and adjust MBR partition 1. Do this in bash for the $'\x...' gestures: # Create the playground cp boot-grub2-f36.iso test.iso # Zeroize the main GPT dd if=/dev/zero bs=1 seek=512 count=32256 conv=notrunc of=test.iso # Zeroize the header block of the backup GPT dd if=/dev/zero bs=512 seek=1334219 count=1 conv=notrunc of=test.iso # Set the boot flag to MBR partition 1 echo $'\x80' | dd bs=1 seek=446 count=1 conv=notrunc of=test.iso # Change the partition type to 0x17 (as with BIOS-only ISOLINUX isohybrid) echo $'\x17' | dd bs=1 seek=450 count=1 conv=notrunc of=test.iso # Set the start of MBR partition 1 to LBA 64, so that it is mountable echo $'\x40' | dd bs=1 seek=454 count=1 conv=notrunc of=test.iso # Append 63 blocks of 512 bytes to compensate for the new start LBA # with the old partition size. (Else partition editors will hate the # image because it is too small for the partition.) dd if=/dev/zero bs=512 count=63 >>test.iso Check whether partition editors like the result and see the boot flag: $ /sbin/fdisk -l test.iso ... Disklabel type: dos ... Device Boot Start End Sectors Size Id Type test.iso1 * 64 1334282 1334219 651.5M 17 Hidden HPFS/NTFS Put test.iso onto the USB stick as usual. The result is supposed to boot from USB stick only via legacy BIOS. EFI would still see the System Partition on a CD or DVD because it is announced by the El Torito catalog. If it does not boot on the Dell XPS 15 L502X, try whether it boots on some other BIOS machine. I only roughly tested that qemu-system-x86_64 -enable-kvm -m 512 -hda test.iso boots to the GRUB menu. Have a nice day :) Thomas _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
