Re: simple message under BIOS/CSM/LEGACY

[lacsaP Patatetom]

Le jeu. 6 juil. 2023 à 16:20, Michael D. Setzer II <mikes@guam.net> a
écrit :

> On 6 Jul 2023 at 15:17, lacsaP Patatetom wrote:
>
> From:   lacsaP Patatetom <patatetom@gmail.com>
> Date sent:      Thu, 6 Jul 2023 15:17:14 +0200
> Subject:        Re: simple message under BIOS/CSM/LEGACY
> To:     help-grub@gnu.org
>
> > Le lun. 21 nov. 2022 à 10:22, Pascal <patatetom@gmail.com> a écrit :
> >
> > > hi,
> > >
> > > I'm coming back on this subject (eg. display a short message inviting
> the
> > > user to switch the PC to EFI/UEFI) after some field feedback.
> > >
> > > here is the simple code now used :
> > >
> > > ; nasm nobioscsm.asm -f bin -o nobioscsm
> > > bits 16
> > > org 0x7C00
> > > start:
> > >     sti
> > >     cld
> > >     mov si, msg
> > >     mov ah, 0x0E
> > >     .loop lodsb
> > >     or al, al
> > >     jz halt
> > >     int 0x10
> > >     jmp .loop
> > > halt:
> > >     hlt
> > >     jmp halt
> > > msg:
> > >     db 0x0D, 0x0A, 'Boot with BIOS/CSM/LEGACY no longer supported :
> reboot
> > > with EFI/UEFI', 0
> > >
> > > and here is what appears on the screen (Lenovo Thinkcenter M720)
> instead
> > > of the expected message :
> > >
> > > [image: clover.jpg]
> > >
> > >
> > > the problem occurs mainly with the Lenovo brand (Thinkcentre M70
> > > <https://www.google.com/search?q=Lenovo+Thinkcenter+M70>, Thinkcentre
> M720
> > > <https://www.google.com/search?q=Lenovo+Thinkcenter+M720>), but not
> only
> > > according to my information.
> > >
> > > changing the partitioning to BIOS/Intel/MBR (instead of GPT) does not
> > > change the problem : this last point makes me strongly believe that the
> > > problem comes from the code...
> > >
> > > regards, lacsaP.
> > >
> > > Le mer. 3 août 2022 à 23:50, Pascal <patatetom@gmail.com> a écrit :
> > >
> > >> thanks for the track of the second active partition (as Ubuntu does
> > >> according to exchanges on the syslinux mailing list).
> > >> I'll try it, but I'm wondering if I'm not going to abandon GPT
> > >> partitioning in favor of DOS partitioning which remains fully
> operational
> > >> under UEFI...
> > >>
> > >> Le mer. 3 août 2022 à 20:25, Pascal Hambourg <pascal@plouf.fr.eu.org>
> a
> > >> écrit :
> > >>
> > >>> Le 03/08/2022 à 16:11, Pascal a écrit :
> > >>> > *this is python biting its tail ;-)*
> > >>> >
> > >>> > here is what I plan to test :
> > >>> > leave the protective partition in place (1), mark it as active (2)
> and
> > >>> > change its first sector to zero (3).
> > >>> >
> > >>> > 1) its absence seems to be a problem (at least with qemu/ovmf),
> > >>>
> > >>> The GPT scheme is usually not recognized without a protective
> partition.
> > >>>
> > >>> > 2) gdisk does not activate it by default,
> > >>>
> > >>> As expected. Setting the boot flag on the protective partition is
> > >>> against the EFI specification.
> > >>>
> > >>> Also, some UEFI firmware refuse to boot in EFI mode if the protective
> > >>> partition has the boot flag set. Setting the boot flag on another
> (even
> > >>> empty) partition entry has given good results with both legacy and
> EFI
> > >>> boot.
> > >>>
> > >>> > the only point that seems contentious to me is whether a partition
> can
> > >>> have
> > >>> > its first sector set to zero ?
> > >>>
> > >>> In the MBR/DOS partition scheme, it should not because the first
> sector
> > >>> is reserved for the MBR (but in Sun/BSD disklabel, partition 'c'
> starts
> > >>> at sector 0 and covers the whole drive). But Debian installation
> images
> > >>> for x86 are set up this way :
> > >>>
> > >>> Device Boot Start     End Sectors  Size Id Type
> > >>> sdb1   *        0 1320959 1320960  645M  0 Empty
> > >>> sdb2         4288   13343    9056  4,4M ef EFI (FAT-12/16/32)
> > >>>
> > >>>
> > >>> > does the BIOS check this kind of thing ?
> > >>>
> > >>> Not in my experience, but I haven't used the Debian installer with
> all
> > >>> existing firmware.
> > >>>
> > >>>
> > hi,
> >
> > a little feedback on this subject we broached last year.
> >
> > I think I've identified the problem, which is linked to the workstation's
> > UEFI, which "jams" when the GPT is "malformed".
> > so, the problem has nothing to do with the little piece of code designed
> to
> > display the warning...
> >
> > the USB media is initially "burned" with a small disk image in GPT
> format :
> > the GPT defined in this small disk image is no longer valid for this USB
> > media once the disk image has been dropped onto it (for example, the
> backup
> > copy expected at the end of the USB media is not there or is not the
> right
> > one).
> >
> > disk image
> > [[GPT#1][P1 NTFS][P2 ESP][GPT#2]]
> > USB media
> > [[GPT#1][P1 NTFS][P2 ESP][GPT#2]             ]
> > - or -
> > [[GPT#1][P1 NTFS][P2 ESP][GPT#2]      [OLD#2]]
> >
> > the same USB media "initialized" (this initialization, performed in
> > initramfs at first boot, consists in repartitioning the USB media to
> occupy
> > all its space) on a second workstation that does not pose this problem,
> > then no longer poses a problem on the first workstation.
> >
> > USB media initialized
> > [[GPT#1][P1 NTFS:::::::::::::][P2 ESP][GPT#2]]
> >
> > the repartitioning operation "corrects" the GPT and the recalcitrant
> > workstation is no longer recalcitrant following this correction.
> >
> > I hope I've made my explanations clear.
> >
> > regards, lacsaP.
> >
> > (ps : I still don't have any recalcitrant workstation available)
> >
>
> Don't know if this would apply to this.
> I create a 64M image file that has GPT disk and contains both a
> regular grub4dos boot and a grub4dos-efi boot to load files.
> Copy the image to a flash using dd and the GPT has the problem
> mentioned.
> Use this to correct it.
> echo -e "Fix" | parted -l ---pretend-input-tty
>
> Believe that looking at flash with gparted also prompts to fix it,
> but the parted -l is much faster.
>
> Perhaps has nothing to do, but thought worth mentioning.
>
>
>
> +------------------------------------------------------------+
>  Michael D. Setzer II - Computer Science Instructor (Retired)
>  mailto:mikes@guam.net
>  mailto:msetzerii@gmail.com
>  Guam - Where America's Day Begins
>  G4L Disk Imaging Project maintainer
>  http://sourceforge.net/projects/g4l/
> +------------------------------------------------------------+
>
>
>
>
thanks for the feedback.

would you know of a similar command under Windows that could fix the GPT ?
with a native Windows tool if possible (diskpart KO, cmdlet KO, what
else...) ?
or even with a small third-party console tool ?

I use this script (https://github.com/patatetom/PowerShellBurner) to put my
disk image on the USB media : I'd just have to add a few commands at the
end to update the GPT...

regards, lacsaP.