Re: Regarding the boot process.

[Riza Dindir <riza.dindir%gmail.com@localhost>]

Hello

On Fri, Sep 3, 2021 at 11:43 PM Michael van Elst <mlelstv%serpens.de@localhost> wrote:
>
> riza.dindir%gmail.com@localhost (Riza Dindir) writes:
>
> >> bootme is used by the EFI bootloader to select the boot partition.
> >> If that flag isn't set, there is a heuristic to select a boot partition.
>
> >How does the system decide which partition to select. I wanted to
> >understand how the system is able to boot from the NetBSD HDD when
> >connected via USB, and also when connected (without any other disks)
> >at the internal HDD sata slot (on its own) and when connected at the
> >DVD sata slot (on its own). Since in these cases, I was able to boot
> >NetBSD from the HDD.
>
> The bootloader just looks for a partition, it doesn't search the boot disk.
> I wouldn't rule out an UEFI bug.
>
>
> >I could not find biosboot in the manual pages, but there is a manual
> >page for the installboot utility that uses a biosboot file.
>
> gpt has a biosboot command and 'gpt set' lets you add a 'biosboot'
> attribute to a partition.
>
>
> >So since this flag is set, would it be possible that the system might
> >be able to boot from the HDD caddy, by only changing this flag to
> >"bootme"?
>
> You can try, but the only thing that 'bootme' should determine is what
> partition the EFI bootloader will select as default. A second disk
> should not have an effect.
>

I did add the bootme flag to the attributes of the netbsd partition on
the disk. The disk had the biosboot and the bootme flag. But now I can
boot the disk using usb. And when i run the bios bootmenu, the disk is
not seen. On Windows I was able to see the disk before the attribute
change. Now the disk does not show up.

I tried to boot the installation disk and drop to the shell. But it
turns out the installation disk does not mount the usb drive. I
thought I could use the installation CD to drop to the shell and use
the gpt tool to remove the bootme flag. Very interesting.

Adding the bootme flag to the attributes of the partition where netbsd
is, would this affect the way this disk is seen by the firmware, or by
the uefi system/logic?

Is this bootme flag something specific to netbsd, or is it something
defined in the uefi specifications?

May this change of attribute corrupt the partition?

Regards,
Riza