Windows 10 problem with GRUB

michota32

11/18/23, 8:05 PM

I've had a dual boot windows 10-Ubuntu for a couple of months, and yesterday out of nowhere i saw that i can't boot into my Windows. Grub is not detecting it.

Over this months i had similar problems, but running

sudo update-grub

and with help of boot repair, i was able to fix those problems. But now it is different, running boot repair, an error message appears saying:

LegacyWindows detected. Please enable BIOS-compatibility/CSM/Legacy mode in your UEFI firmware, and use this software from a live-CD (or live-USB).

The thing is, when I installed ubuntu, I checked that it was with the same boot method as Windows (both on UEFI, i think). Otherwise, the dual boot would never have been able to work all of this time.

Here's a list of things that I already tried:

Running sudo update-grub
Running repair boot
Check if fast boot and secure boot are disabled in my BIOS
Disabling CSM in my BIOS

And nothing worked. The folder /sys/firmware/efi/ exists in my Ubuntu, so I assume that now is on UEFI mode. Running sudo os-prober returns nothing (even with all of the disks mounted).

I'm pretty noob with ubuntu, sorry if I said something dumb. Can Windows turn into Legacy boot out of nowhere?. I generated a paste bin from boot repair, in case that may help: https://paste.ubuntu.com/p/Vq3HnH9xSS/

174

0 + 2

boot

grub2

dual-boot

windows

uefi

Nmath

11/18/23, 8:14 PM

*"Can Windows turn into Legacy boot out of nowhere"* - This is a question for the Windows community, but I think the answer is probably "No". In any case, Ubuntu and Windows must both be installed in the same mode or else you'll encounter problems with dual boot configuration and GRUB. If Windows is CSM and Ubuntu is EFI you'll need to change one of them, preferably switching Windows to EFI. Unfortunately this generally requires reinstalling the OS.

oldfred

11/18/23, 8:45 PM

Grub does not use boot flag, Windows has to have boot flag on its partition with boot files. But not sure if your Windows is booting from sda1 or sdb1. And then you cannot have an ESP - efi system partition on same drive as it also needs boot,esp flags. Move boot flag back to sdb1 with gparted or Windows. Better to have grub in MBR of one drive and Windows boot loader in the other. Use Boot-Repair's advanced mode. Best to have both systems in UEFI mode as Microsoft required vendors to install in UEFI/gpt mode since 2012. But conversion from MBR to gpt will erase entire drive. Backups required.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Windows 10 problem with GRUB

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.