Need Help Restoring Grub on Dual OS System

[Gary1964]

Hi:

I wish to restore my Grub configuration, as it was corrupted after a recent Windows 11 update.
The disk configuration of this dual boot system is:

To summarize, I have Windows11 on /dev/nvme0n1:
Disk /dev/nvme0n1: 1.82 TiB, 2000398934016 bytes, 3907029168 sectors
Disk model: KINGSTON SNV2S2000G
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: A331EDC9-2761-4617-A787-A5C72F3753BD

Device Start End Sectors Size Type
/dev/nvme0n1p1 2048 206847 204800 100M EFI System
/dev/nvme0n1p2 206848 239615 32768 16M Microsoft reserved
/dev/nvme0n1p3 239616 3905478655 3905239040 1.8T Microsoft basic data
/dev/nvme0n1p4 3905478656 3907028991 1550336 757M Windows recovery environment

Kubuntu is on /dev/nvme1n1:
Disk /dev/nvme1n1: 1.82 TiB, 2000398934016 bytes, 3907029168 sectors
Disk model: KINGSTON SNV2S2000G
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 4E79B735-A6FB-408A-8A11-17446E8F1747

Device Start End Sectors Size Type
/dev/nvme1n1p1 34 32767 32734 16M Microsoft reserved
/dev/nvme1n1p2 32768 1953529856 1953497089 931.5G Microsoft basic data
/dev/nvme1n1p3 1953529858 3907026943 1953497086 931.5G Linux filesystem

These are the commands that I think that I am supposed to execute:
kubuntu@kubuntu:~$ sudo mount /dev/nvme1n1p3 /mnt
kubuntu@kubuntu:~$ sudo mount /dev/nvme0n1p1 /mnt/boot/efi
kubuntu@kubuntu:~$ sudo mount --bind /dev /mnt/dev
kubuntu@kubuntu:~$ sudo mount --bind /proc /mnt/proc
kubuntu@kubuntu:~$ sudo mount --bind /sys /mnt/sys
kubuntu@kubuntu:~$ sudo chroot /mnt

I believe that I am supposed to next execute grub-install. However, I am unsure of the input argument to
enter along with the 'grub-install' command. Is it simply:

root@kubuntu:/# grub-install /dev/nvme1n1

Is this even the correct approach or do these steps need to be amended?

Thanks in advance,

Gary

[claydoh]

Are you sure that the Win update didn't just change your BIOS boot order? Happens quite often and worth checking before messing with things.

[Qqmike]

Follow what claydoh has in mind.

For reference, FWIW, my how-to on chroot and your options:
Re-install GRUB2 from Live DVD/USB flash drive
https://www.kubuntuforums.net/forum/...l=1#post537598

chrooting always seems to be a crapshoot, IMO; only an expert (not me) really knows what you should "bind," but it often seems to work no matter.
Boot-Repair is an option. But pay attention to what claydoh says before you dive in.
Complication: Do you have 1 or 2 ESPs? If only 1, the grub-install command should find it ok: "sudo grub-install"
Can you boot into Kubuntu using your Windows boot loader, and then simply issue "sudo grub-install"? (and then "sudo update-grub")