Neon system grub boot error -- can I devine what to do? /dev/?

[pwrcul]

Please tell me if I need to take this elsewhere at Kubuntu forum or elsewhere outside as it is a grub issue growing out of my Neon boot failure problem.

As forum regulars know, I have a Neon system that does not boot. I backed up key files and now am hoping to try some ways to get it to boot enough to try to fix it.
I am following this guide: https://www.linuxfoundation.org/blog...rub-2-on-linux

I end up first in grub and then in (initramfs).
The error message I get has to do with /dev/sdc3 does not exist after boot fails when it stops waiting for missing boot files.
My guess is that is that /dev/sdc3 is where /boot and root are, i.e., (hd2,gpt3) on my system.
Maybe I just misunderstand that part, how (hd2,gpt3) is expressed, as /dev/sdc3 or something else?
I had begun with ls and then ls (hd2,gpt3)/ to find root and boot/grub as in the guide.

[Schwarzer Kater]

I think this is the right forum and one of the best forums for KDE neon users.

Perhaps begin with telling us what the output of ls in the GRUB CLI is, which drives you do have in your computer and on which partitions you did install what before?

The exact error message(s) would also be a good thing to post here…

[pwrcul]

Ok, Schwarzer Kater.

the prompt is grub>

ls gets (hd0) (hd0,msdos3) (hd0,msdos2) (hd1) (hd1,msdos3) (hd1,msdos2) (hd2) (hd2,gpt3) (hd2,gpt2) (hd2,gpt1)
ls (hd2,gpt3)/ gets ./ ../ lost+found/ dev/ proc/ run/ sys/ bin lib lib32 lib64 libx32 sbin /boot etc/ home/ media/ mnt/ opt/ root/ snap/ srv/ tmp/ usr/ var/

I will crash and get back....

[pwrcul]

Commands sent to Grub

grub> set pager=1
grub> set root=(hd0,1)
grub>; linux /boot/vmlinuz-3.13.0-29-generic root=/dev/sda1
grub>; initrd /boot/initrd.img-3.13.0-29-generic
grub> insmod normal
grub> normal
grub> insmod linux
grub> boot

[pwrcul]

The above commands include a typo (from the previously mentioned guide)
Here is a corrected replacement set:

grub> set pager=1
grub> set root=(hd2,gpt3)
grub> linux /boot/vmlinuz-5.15.0-48-generic root=/dev/sdc3
grub> initrd /boot/initrd.img-5.15.0-48-generic
grub> insmod normal
grub> normal
grub> insmod linux
grub> boot

[Schwarzer Kater]

Unfortunately I don't have any time now to take a closer look, but shouldn't there be at least
insmod part_gpt
insmod ext2 (or insmod btrfs if you use btrfs)
before you set root etc.?

[pwrcul]

Here are the responses to the above including error messages:

Begin: Waiting for root file system ... Begin: Running /scripts/local-block ... done.
done.
Gave up waiting for root file system device, Common Problems:
- Boot args (cat /proc/cmdline)
- Check rootdelay=(did the system wait long enough?)
- Missing modules (cat /proc/modules; ls /dev)
ALERT! /dev/sdc3 does not exist. Dropping to a shell!

BusyBox v1.30.1 (Ubuntu 1.1.30.1-7ubuntu3) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs)

End of response messages.
I followed all the suggestions. I think the one with most promise is /dev/sdc3 does not exist.
But if I got that wrong, what would be the correct /dev/ statement?

[pwrcul]

I just saw Schwarzer Kater's earlier response.
I will look into the insmod suggestions.
My file systems is ext4.

[Snowhog]

ALERT! /dev/sdc3 does not exist.

This is the root of your problem. GRUB is looking for /dev/sdc3 and that device/partition doesn't exist. Obviously, it did 'at one time'. When you reboot your PC, are you presented with a GRUB Menu?

[pwrcul]

When I do Ctrl-Alt-Del I get the grub command line interface. I am hoping to get the Grub Menu.
I believe it is the same if I type reboot

Did I understand correctly how to express (hd2,gpt3)? As /dev/sbdc3 ?
In the above Linux Foundation guide they say:
grub>; set root=(hd0,1)
grub> linux /boot/vmlinuz-3.13.0-29-generic root=/dev/sda1
grub> initrd /boot/initrd.img-3.13.0-29-generic
grub> boot

The first line sets the partition that the root filesystem is on. The second line tells GRUB the location of the kernel you want to use. Start typing /boot/vmli, and then use tab-completion to fill in the rest. Type root=/dev/sdX to set the location of the root filesystem. Yes, this seems redundant, but if you leave this out you’ll get a kernel panic. How do you know the correct partition? hd0,1 = /dev/sda1. hd1,1 = /dev/sdb1. hd3,2 = /dev/sdd2. I think you can extrapolate the rest.

[Schwarzer Kater]

This is the root of your problem. GRUB is looking for /dev/sdc3 and that device/partition doesn't exist. […]

How about using something like "… root=f8a18405-442d-472c-bb00-766128822afd" (replace the UUID with the actual one, of course…)?

PS: And perhaps set a --fs-uuid before (but I am not sure if this is necessary).

[pwrcul]

Following the suggestion to try
insmod part.gpt
insmod ext2
before the set boot command
I entered the following while the new error message appears (here presented in bold)

set pager=1
insmod part.gpt
error: file '/boot/grub/x86_64-efi/part.qpt.mod not found

insmod ext2
grub> set root=(hd2,gpt3)
grub> linux /boot/vmlinuz-5.15.0-48-generic root=/dev/sdc3
grub> initrd /boot/initrd.img-5.15.0-48-generic
grub> insmod normal
grub> normal
grub> insmod linux
grub> boot

The error message was the same

Begin: Waiting for root file system ... Begin: Running /scripts/local-block ... done.
done.
Gave up waiting for root file system device, Common Problems:
- Boot args (cat /proc/cmdline)
- Check rootdelay=(did the system wait long enough?)
- Missing modules (cat /proc/modules; ls /dev)
ALERT! /dev/sdc3 does not exist. Dropping to a shell!

BusyBox v1.30.1 (Ubuntu 1.1.30.1-7ubuntu3) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs)

I remain baffled.

[Schwarzer Kater]

part_gpt - not part.gpt

[Schwarzer Kater]

As an example this is what (part of) my GRUB boot entry for KDE neon looks like:

insmod part_gpt
insmod ext2​
set root='hd0,gpt6'
search --no-floppy --fs-uuid --set=root a35618a9-6db5-4495-a8cf-722c4ffe4b2a
linux /boot/vmlinuz-5.19.0-46-generic root=UUID=a35618a9-6db5-4495-a8cf-722c4ffe4b2a
initrd /boot/initrd.img-5.19.0-46-generic

Perhaps that will help (and remember that the guide you are referring to is quite old: "This is a classic article written by Carla Schroder from the Linux.com archives.").

At the GRUB command line I would probably also add insmod linux and possibly insmod normal and insmod gzio right at the beginning, and boot at the end of course.

PS: But I don't quite understand the whole thread…
Why don't you just chroot from another system that is booted from a live USB or use something like the rescue mode from the Debian installation DVD-1 to graphically chroot into your broken KDE neon to repair your GRUB and anything else that needs repairing?

[pwrcul]

I made the correction to my typo that Schwarzer Kater wanted so it now has
insmod part_gpt
That statement is accepted.

Alas the ALERT! /dev/sdc3 error is still with us....

Although I don't like it, I am thinking of bracketing /dev/sdc3 with /dev/sdc2 /dev/sdc4 /dev/scc3 /dev/scc2 to provoke messages
Reading grub documentation may help more?