Le 07/10/2025 à 23:04, Antoine a écrit :
> On Tuesday,  7 October at 09:47, Hendrik Boom wrote:
>> (...)>
>> Isn't there another piece of bootloader outside the file system at
>>  the very beginning of the boot disk?
>>  Especially if using lilo?
>> And isn't there a DOS partition that's used by the new-fangled bootup
>>  system that replaced legacy boot and that the Wintel copanies have
>>  imposed on us?  I've never figured out where its content is supposed
>>  to come from.
>>
>> -- hendrik
>
> Originally, the BIOS bootloader was in the first 512 bytes of the boot
> disk - the Master Boot Record or boot sector. These days, bootloaders
> are bigger (and more complicated) so grub has an initial image which
> is witten to the boot sector, which then passes control to a bigger
> and more complicated image which is usually written to an unformatted
> partition. This is then able to read your filesystem, load the main
> part of grub, your grub.conf and so on.

    Is the bigger part of Grub stored into a non-formatted partition,
or a free space of the device (some space which is not allocated by the
partition table)?

    As I could read on the Internet, if you have a DOS-type, also
called MBR, partition table, you need to preserve free space before the
first partition, which is what I've done since the advent of Grub2, but
if you use a GNU Partition Table, you need a Grub-dedicated
non-formatted partition. However I don't know how the last is possible,
because my little experience with GPT is that you need parted to crate
it and parted automatically formats all the partitions. Is there a
specific Grub partition type?

    Does anyone have a comprehensive explanation?

--     Didier