Tested this iso with an USB stick on this machine here and it passed the tests and Anaconda started correctly.
Machine: Type: Laptop System: Hewlett-Packard product: HP G42 Notebook PC Mobo: Hewlett-Packard model: 1484 v: 77.19 BIOS: Hewlett-Packard v: F.17 date: 07/06/2010
CPU Dual core Pentium T4500 2.3GHz
RAM 6GB
Geraldo Simião
@geraldosimiao:matrix.org
Em seg, 18 de abr de 2022 14:44, Thomas Schmitt <scdbackup@xxxxxxx> escreveu:
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
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