[RESOLVED] Where are UUIDs stored?

[joneall]

Yesterday, I re-installed a fresh 24.04 system and configured stuff like firefox and libreoffice. This morning, I cannot boot it. It bombs with

ALERT! UUID=668... does not exist.

But when I boot another system and then mount the root partition for the defective system, blkid finds no partition with that UUID. In order to identify the problem, one lead seems to me to be what in the world that partition is, i.e., what /dev/sd-something it corresponds to. So how do I go about finding that?

I plugged in and mounted the installation USB key, which came up as sde, but nothing shows up the UUID's for sde. Are they not stored somewhere on the partition? I certainly can't find it with gdisk.

I have re-booted both those systems since installation and they worked fine. Mystery.

[joneall]

I have discovered the file command and run 'sudo file -sL /dev/sd,,,,/ on all my partitions. No UUID=66...

[joneall]

Strictly speaking, this query is resolved, since I found out how to find the UUID for a device /dev/sdx.

[claydoh]

use the command blkid

But if , as a random, pulled-out-of-my-butt example: you have an old entry in your BIOS that points to an old partition for some reason, and your BIOS boot order is set to that stale entry
I am assuming you see this error early on, and do not get to grub.

If you moved or resized partitions since installing (not likely) that would obviously change that partition's UUID

[joneall]

But if , as a random, pulled-out-of-my-butt example: you have an old entry in your BIOS that points to an old partition for some reason, and your BIOS boot order is set to that stale entry
I am assuming you see this error early on, and do not get to grub.

Actually, it has displayed several screenfulls of boot log by then. In fact, syslog shows lines like this:

Oct 14 15:14:03 jon-desktop 40grub2: debug: parsing: menuentry 'KDE neon 6.2 GNU/Linux, with Linux 6.8.0-45-generic (recovery mode) (on /dev/sdb2)' --class gnu-linux --class gnu --class os $menuentry_
id_option 'osprober-gnulinux-/boot/vmlinuz-6.8.0-45-generic-root=UUID=668e8ec0-4a8c-4fec-87dd-4fb5468ab9ec ro recovery nomodeset dis_ucode_ldr-668e8ec0-4a8c-4fec-87dd-4fb5468ab9ec' {
Oct 14 15:14:03 jon-desktop 40grub2: debug: parsing: linux /boot/vmlinuz-6.8.0-45-generic root=UUID=668e8ec0-4a8c-4fec-87dd-4fb5468ab9ec ro recovery nomodeset dis_ucode_ldr

Whatever does that mean? What is this menuentry jazz? Looks like the grub cfg file is corrupted. Where do I find that and fix it?

If you moved or resized partitions since installing (not likely) that would obviously change that partition's UUID

Really? That surprises me. That would be a vote for using label rather than uuid or device name in fstab.

[claydoh]

Really? That surprises me. That would be a vote for using label rather than uuid or device name in fstab.

it doesn't normally, but it *can*, just more stuff I was throwing at the wall.