Hi, i wrote: > > xorrisofs option --mbr-force-bootable Chris Murphy wrote: > with the bit set it means older versions of > Tianocore or anything based on Tianocore up until maybe 6 months ago, > won't boot. Is this maybe about the code snippet of Tianocore which Alexander E. Patrakov showed in the course of the grub-bug thread of 2015/16 ? https://marc.info/?l=grub-bug&m=145052969801875&w=2 " OK, Tiano Core validates the protective partition as follows: // // Verify that the Protective MBR is valid // for (Index = 0; Index < MAX_MBR_PARTITIONS; Index++) { if (ProtectiveMbr->Partition[Index].BootIndicator == 0x00 && ProtectiveMbr->Partition[Index].OSIndicator == PMBR_GPT_PARTITION && UNPACK_UINT32 (ProtectiveMbr->Partition[Index].StartingLBA) == 1 ) { break; } } if (Index == MAX_MBR_PARTITIONS) { goto Done; // i.e. not valid } So here is an alternative suggestion: don't mark the protective partition, create another dummy MBR partition of type 0x00, mark it as bootable. " That's what --mbr-force-bootable does. The shown code will find type 0xEE == PMBR_GPT_PARTITION in partition 1 with boot/active flag == 0x00 and be happy. Others which are more picky will hopefully ignore partitions of type 0x00. UEFI 2.8 , 5.2.1 Legacy Master Boot Record (MBR) says: "The following test must be performed to determine if a legacy MBR is valid: * The Signature must be 0xaa55. * A Partition Record that contains an OSType value of zero or a SizeInLBA value of zero may be ignored." For now, "may be ignored" seems to be enough of protection against trouble. An alternative to --mbr-force-bootable could be to offer a 16-byte file for download together with the instructions to patch it into a pure and specs conformant ISO with GPT. Of course, only if a 10 year old laptop refuses to recognize the original ISO on USB stick. The bytes would have to be { 128, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0 } Assumed the file is named "dummy_mbr_part2.img" the patch instruction would be dd if=dummy_mbr_part2.img of=boot-grub2-f36.iso \ conv=notrunc bs=1 seek=462 count=16 ------------------------------------------------------------------------- Ubuntu is testing this for you since about a year. :)) Afaik the first official ISO of this layout was ubuntu-21.04-desktop-amd64.iso and they did _not_ revoke it half a year later with ubuntu-21.10-desktop-amd64.iso $ xorriso -indev ubuntu-21.10-desktop-amd64.iso -report_system_area plain ... Volume id : 'Ubuntu 21.10 amd64' System area options: 0x00004201 System area summary: MBR protective-msdos-label grub2-mbr cyl-align-off GPT ISO image size/512 : 6086880 Partition offset : 16 MBR heads per cyl : 0 MBR secs per head : 0 MBR partition table: N Status Type Start Blocks MBR partition : 1 0x00 0xee 1 6086879 MBR partition : 2 0x80 0x00 0 1 GPT : N Info ... $ /sbin/fdisk -l ubuntu-21.10-desktop-amd64.iso Disk ubuntu-21.10-desktop-amd64.iso: 2.9 GiB, 3116482560 bytes, 6086880 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: gpt Disk identifier: EF83665C-2F29-48D6-8C3F-80F5A69CFEB7 Device Start End Sectors Size Type ubuntu-21.10-desktop-amd64.iso1 64 6077751 6077688 2.9G Microsoft basic da ubuntu-21.10-desktop-amd64.iso2 6077752 6086215 8464 4.1M EFI System ubuntu-21.10-desktop-amd64.iso3 6086216 6086815 600 300K Microsoft basic da ------------------------------------------------------------------------- Whatever, we do not yet know for sure whether the boot failure with the Dell XPS 15 L502X is caused by the lack of a boot/active flag. We also don't know yet whether the failure with "CD-R and an HP Compaq 8510w" that was reported by Brandon Nielsen is due to drive-media problems with the CD-R or due to problems with the ISO. 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
