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List:       gentoo-user
Subject:    Re: [gentoo-user] updating /boot directory EFI
From:       Michael <confabulate () kintzios ! com>
Date:       2023-04-17 17:10:37
Message-ID: 2226267.3ZeAukHxDK () lenovo ! localdomain
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On Monday, 17 April 2023 17:52:25 BST Mark Knecht wrote:

> One thing I haven't decoded is why Windows is 0000 and Kubuntu is 0003.

See below ...


> I now better understand Mitch D.'s point that the pointers to which OS to
> boot are not in a disk file, like the old grub configuration, but rather in
> Flash memory on the motherboard. I suppose the numbering is just the
> luck of the draw, or that 0001 and 0002 were used at one time and no longer
> present, but that's just a guess.

Exactly the latter, they are no longer present.  I copy kernel images manually 
to /boot/EFI/Gentoo/ and run 'efibootmgr --create' to add entries to the UEFI 
boot menu with my choice of labels.  They are added being numbered 
incrementally.  If I remove some of the older menu entries, their 
corresponding numbers are also removed and become available for any new 
bootable .efi images I may add in the future.

In addition, if I boot with any USB drives attached, the UEFI firmware will 
scan such devices and add any bootable images to the UEFI boot menu stored in 
NVRAM, by numbering such images incrementally.  This will further increase the 
numbers of boot menu entries, which once the USB devices are removed their 
entry number will become vacant and available to be reallocated.




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