Hi,
i wrote:
> > Does it boot with ubuntu-21.10-desktop-amd64.iso ?
Dominik 'Rathann' Mierzejewski wrote:
> It doesn't. Same error.
> [...]
> $ grub2-mkrescue -o output-mbr.iso --mbr-force-bootable minimal
> gives me the "Operation System not found" BIOS error again.
> > Building something nearer to the old ISO layout:
> > new_iso=test_mjgappended.iso
> Unfortunately, that one doesn't boot.
So it is really a new BIOS quirk.
It is astounding how much the old jackalope ISO snuggles itself into such
firmwares.
> I'll try modifying the ISO from the beginning of this thread according
> to your instructions from another subthread.
If it is about the variant with options -part_like_isohybrid and
-isohybrid-gpt-basdat then i have to warn of a bug in xorriso which
i found while preparing the next experiment.
The bug prevents the production of the MBR partition table in this case
and thus makes the resulting ISO unbootable on EFI from USB stick.
BIOS booting should be ok. But the wrong result is not a candidate for
a generally bootable ISO. Maybe it is not even significant for a test.
I am currently testing a remedy, but this will last a few days because
i have to be quite paranoid with changing the boot equipment code in
libisofs.
When it's ready, i will ask you to download and compile a GNU xorriso 1.5.5
development snapshot. (The compilation has no special dependencies.)
------------------------------------------------------------------------
Whatever, if you want to try already now with the buggy result, begin
like with the last experiment. You can re-use the files from the
last time:
# Extract the EFI partition
dd if=boot-grub2-f36.iso bs=512 skip=1313268 count=20288 of=test_efi.img
# Extract the MBR code
dd if=boot-grub2-f36.iso bs=1 count=446 of=test_mbr.img
# Pad MBR up to 32768 bytes, so that it overwrites the loaded system area
dd if=/dev/zero bs=1 count=32322 >>test_mbr.img
The xorriso run shall bring the ISO as near to the old layout as possible:
new_iso=test_oldlayout.iso
# xorriso in its native mode does not truncate -outdev
test -e "$new_iso" && rm "$new_iso"
xorriso \
-indev boot-grub2-f36.iso \
-outdev "$new_iso" \
-map test_efi.img /images/efiboot.img \
-as mkisofs \
-part_like_isohybrid \
--grub2-mbr test_mbr.img \
--boot-catalog-hide \
-b /images/eltorito.img \
-no-emul-boot -boot-load-size 4 -boot-info-table \
--grub2-boot-info \
-eltorito-alt-boot \
-e images/efiboot.img \
-no-emul-boot -isohybrid-gpt-basdat \
-R -J \
-- \
-padding included \
-compliance no_emul_toc \
-stdio_sync off
After bug correction the result will look like this:
$ xorriso -indev "$new_iso" -report_system_area plain -report_el_torito plain
[...]
System area options: 0x00004a00
System area summary: MBR grub2-mbr cyl-align-off GPT
ISO image size/512 : 1334000
Partition offset : 0
MBR heads per cyl : 64
MBR secs per head : 32
MBR partition table: N Status Type Start Blocks
MBR partition : 1 0x80 0x17 0 1334000
MBR partition : 2 0x00 0xef 1313032 20288
MBR partition path : 2 /images/efiboot.img
GPT : N Info
GPT disk GUID : 63f762129e2da8499aee97f68461f45f
GPT entry array : 2 248 separated
GPT lba range : 64 1333936 1333999
GPT partition name : 1 490053004f004800790062007200690064003100
GPT partname local : 1 ISOHybrid1
GPT partition GUID : 1 63f762129e2da8499aef97f68461f45f
GPT type GUID : 1 a2a0d0ebe5b9334487c068b6b72699c7
GPT partition flags: 1 0x1000000000000001
GPT start and size : 1 1313032 20288
GPT partition path : 1 /images/efiboot.img
El Torito catalog : 77 1
El Torito images : N Pltf B Emul Ld_seg Hdpt Ldsiz LBA
El Torito boot img : 1 BIOS y none 0x0000 0x00 4 78
El Torito boot img : 2 UEFI y none 0x0000 0x00 20288 328258
El Torito img path : 1 /images/eltorito.img
El Torito img opts : 1 boot-info-table grub2-boot-info
El Torito img path : 2 /images/efiboot.img
$ /sbin/fdisk -l "$new_iso"
[...]
Disklabel type: dos
[...]
Disk identifier: 0x00000000
Device Boot Start End Sectors Size Id Type
test_oldlayout.iso1 * 0 1333959 1333960 651.4M 17 Hidden HPFS/NTFS
test_oldlayout.iso2 1313008 1333295 20288 9.9M ef EFI (FAT-12/16/32)
With the bug still in xorriso, the lines which begin by "MBR" will be
missing. fdisk will report no partitions. (Normal BIOS would not care
about these defects.)
Have a nice day :)
Thomas
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