Re: Do I need to act on this warning from apt when installing grub?

[Pascal]

thank you for all these details Pascal.
good week-end to all.

Le ven. 16 déc. 2022 à 16:48, Pascal Hambourg <pascal@plouf.fr.eu.org> a
écrit :

> On 16/12/2022 at 15:32, Pascal wrote:
> > does this new summary, which takes into account the previous feedback,
> seem
> > "better" to you ?
>
> Yes, better.
>
> > Is the second remark² correct ?
>
> I guess so, as long as the required drivers are embedded in the core
> image and the drive can be read via the BIOS/UEFI. But your diagram of
> EFI boot still shows in inside the ESP.
>
> > is the boot sector of the image directly/readily accessible (eg. editable
> > with hexedit) in the boot sector ?
>
> Not sure I understand what you mean. The MBR is accessible just like any
> other sector.
>
> >              INTEL/MBR                GPT
> >             PARTITIONING          PARTITIONING
> >        ┌─────────────────────┬─────────────────────┐
> >        │MBR 1/3              │MBR 1/3              │
> >        │POST-MBR-GAP 2/3     │                     │
> >        │┌───────────────────┐│┌───────────────────┐│
> >        ││PART               │││PART BIOS-BOOT 2/3 ││
> >        ││/boot/grub/ 3/3    ││└───────────────────┘│
> >   BIOS ││...                ││┌───────────────────┐│
> >   BOOT ││                   │││PART               ││
> >        ││                   │││/boot/grub/ 3/3    ││
> >        ││                   │││...                ││
> >        │└───────────────────┘│└───────────────────┘│
> >        ├─────────────────────┼─────────────────────┤
>
> Note that this is only the standard layout. Other layouts are possible
> such as:
> - a primary boot loader installed in the MBR and chainloads GRUB boot
> image installed in a partition boot sector (PBR)
> - core image installed in a Btrfs filesystem reserved boot area
> - core image installed as a file /boot/grub/i386-pc/core.img (using
> block lists, unreliable)
>
> > # in BIOS mode :
> >    - 1/3 BIOS load and run GRUB boot loader located in the MBR
>
> "GRUB boot image" would be more accurate. "GRUB boot loader" is the
> whole GRUB, not only the boot sector part.
>
> >    - 2/3 GRUB boot loader load and run GRUB core image stored in
> > POST-MBR-GAP (INTEL/MBR) or on BIOS-BOOT partition (GTP)¹
>
> GPT.
>
> >    - 3/3 GRUB core image find and mount the GRUB folder², load
> configuration
> > etc..
>
> GRUB does not really mount filesystems. It just reads them.
> s/folder/directory/. There is no such thing as "folder" in usual
> filesystems.
>
> >
> > # in UEFI mode :
> >    - 1/2 UEFI³ load and run GRUB boot loader located on ESP⁴
>
> "GRUB core image" would be more accurate. "GRUB boot loader" is the
> whole GRUB (including modules in /boot/grub), not only the core image.
>