On Wed 13/03/2024 at 12:50, Michel Verdier <mv...@free.fr> wrote:
> On 2024-03-13, Gareth Evans wrote:
>
>> That suggests perhaps something to do with an FS UUID, but it doesn't seem
>> to appear in the output of any of
>>
>> # blkid
>
> Here I have them shown as UUID by blkid
>
> # grep root /boot/grub/grub.cfg
> ...
> search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt2
> --hint-efi=hd1,gpt2 --hint-baremetal=ahci1,gpt2
> 5210342e-548e-4c4d-a0e9-a5f6d13888d6
> ...
>
> # blkid|grep -i 5210342e
> /dev/sdb2: UUID="5210342e-548e-4c4d-a0e9-a5f6d13888d6" ...
>
> hint-bios=hd0,gpt3 suggests its your 3rd partition on your first disk.
>
> Do you use raid ?
Hi Michael,
I'm currently using a single disk with ZFS, partitioned as
$ sudo fdisk -l /dev/sda
<snip>
Disk identifier: 3405...
Device Start End Sectors Size Type
/dev/sda1 48 2047 2000 1000K BIOS boot
/dev/sda2 2048 1050623 1048576 512M EFI System
/dev/sda3 1050624 3147775 2097152 1G Solaris /usr & Apple ZFS
/dev/sda4 3147776 250069646 246921871 117.7G Solaris root
$ sudo grep root /boot/grub/grub.cfg
<snip>
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt3
--hint-efi=hd0,gpt3 --hint-baremetal=ahci0,gpt3 9cbef743dfafd874 <------
<snip>
$ sudo blkid|grep 9cbe
$
$ lsblk -o MODEL,NAME,LABEL,WWN,UUID,SERIAL,PTTYPE,PTUUID,PARTUUID|grep 9cbe
$
/# ls -R|grep 9cbe
some filenames contain a match to the substring searched for, but none match
the 16-digit hex number fully.
This excludes it appearing in any of the /dev/disk/by-*/ identifiers, which I
have also checked separately just in case.
I git cloned grub to see if I could make sense of how grub.cfg is generated.
$ git clone https://git.savannah.gnu.org/git/grub.git
According to NEWS for v1.97:
> * update-grub is replaced by grub-mkconfig
So after making some sense of grub-mkconfig.in, it turns out the 16-digit hex
number is returned by
# grub-probe --device /dev/sda3 --target=fs_uuid
9cbef743dfafd874
Given that the above command fails with
--device /dev/sda4
(which is the running system's /), gpt3 appears to be sda3, ie. the boot
partition, so
--set=root
in the grub.cfg search line presumably relates to the root of /boot.
I'm still curious as to why it doesn't seem to appear anywhere else, how it was
applied, and what exactly it applies to - a filesystem? This is not aiui the
usual form of a UUID either.
grub-probe.in or grub-install.c might hold answers. I will reply again if I
discover anything informative.
Thanks,
Gareth
