On Mon, Apr 17, 2023 at 8:18 AM Michael <confabul...@kintzios.com> wrote:
>
> On Monday, 17 April 2023 14:31:08 BST Mark Knecht wrote:
<SNIP>
> > 2) The more complicated view with GUIDs and such:
> >
> > mark@science2:~$ efibootmgr -v
> > BootCurrent: 0003
> > Timeout: 1 seconds
> > BootOrder: 0003,0000
> > Boot0000* Windows Boot Manager
> > HD(1,GPT,2052c843-0057-494a-a749-e8ec3676514a,0x800,0x32000)/File(\EF
> >
I\MICROSOFT\BOOT\BOOTMGFW.EFI)WINDOWS.........x...B.C.D.O.B.J.E.C.T.=.{.9.d.
> > e.a.8.6.2.c.-.5.c.d.d.-.4
> > .e.7.0.-.a.c.c.1.-.f.3.2.b.3.4.4.d.4.7.9.5.}....................
> > Boot0003* ubuntu
> >
HD(1,GPT,2052c843-0057-494a-a749-e8ec3676514a,0x800,0x32000)/File(\EFI\UBUN
> > TU \SHIMX64.EFI)
> > mark@science2:~$
>
> This shows the efibootmgr is using the first disk and boots the Windows
> BOOTMGFW.EFI, or Ubuntu's shimX64.efi from there.
OK, that part makes perfect sense and the files are there.
Additionally the GUID in each HD(...) entry matches the GUID on
/dev/nvme0n1p1
which has a type "EFI system partition" in fdisk. Good so far.
<SNIP>
> > The 'problem' with this setup is that all of the grub/efibootmgr stuff
> > is on both drives
>
> Are you sure?
Yes, there is a directory but that directory, which did have a Kubuntu
boot image in the past, is now empty.
HISTORY. I bought the computer with Win 10 installed and a
second empty M.2 drive. To install Kubuntu I switched BIOS to
boot from that drive, installed Kubuntu which populated the EFI
directory with all of the stuff you're showing me. I did not know about
the efibootmgr at the time as this was my fist new MB in about 8
years.
Early on I went to Windows by changing BIOS because, for what
ever reason the Kubuntu install didn't see the Windows disk. I
am assuming that was probably me completely disabling it in
BIOS but I don't remember the details.
Later on a Kubuntu update found Windows, updated the EFI
stuff on the Windows drive and then, I see this morning,
erased everything out of the Kubuntu EFI partition but
left the partition there.
<SNIP>i
>
> This is where the ESP is mounted, but you'll find /boot directory is on
your /
> dev/nvme1n1p3 block device, along with your kernels, initrd images and
> vimlinuz symlinks.
>
Correct.
ESP? EFI System Partition possibly?
> Your GRUB EFI bootable image is on /dev/nvme0n1p1, under
/boot/efi/EFI/ubuntu/
>
> > tmpfs 3.2G 64K 3.2G 1% /run/user/1000
> > mark@science2:~$
>
> I would think Ubuntu installed GRUB on nvme0n1p1 ESP, which it detected by
> scanning your disks. If your nvme0n1p1 fails and has to be removed, you
will
> need to create a new ESP somewhere on the ubuntu disk and then you can
> reinstall GRUB after you reboot with a LiveUSB, or while still running
ubuntu.
Understood. Thanks.
One thing I haven't decoded is why Windows is 0000 and Kubuntu is 0003.
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.
For anyone following along or reading later, there's an easily read web page
on things you can do with efibootmgr located here:
https://www.linuxbabe.com/command-line/how-to-use-linux-efibootmgr-examples
Also, the Windows app similar to efibootmgr (but untested by me) is
possibly called bootcfg.exe
- Mark
