Grub and 2x windows on 1 gpt drive (uefi)

Tomáš Vaňoch

8/12/24, 10:23 PM

first, sorry for my english. Can somebody help with grub? I updated from mbr to gpt and now i have broken grub. I need to be able to select in grub menu which OS i want to start. Now i have only option to select "windows" and then i selecting again which windows i want to start.. This is bad.. I need to select in grub what os to start and no more selecting anything. grub loading bootmgfw.efi file and every windows share this file. How i can separate this? Make for example 2bootmgfw2.efi file for second windows to be able start into system directly from grub and not going into windows boot manager. Go around, or somehow tell to bootmgfw.efi boot directly into system one (or two) and i dont want to select anything anymore.. Is it possible? (im sure it is, I had this on my mbr system working perfectly, but im not able to replicate this on gpt without help.

For easy example, when I have this in grub.cfg

insmod part_gpt

insmod chain

set root=(hd0,gpt1)

chainloader /EFI/Microsoft/Boot/bootmgfw.efi

boot

Can i add some parameter in this code to tell what specific OS i want to start and skip that selecting in ugly, black, text windows bootmanager?

0 + 1

boot

grub2

windows

grub-efi

oldfred

8/13/24, 5:57 PM

You have to create a temportary ESP, and do a repair install of Windows so it creates the Windows boot files & BCD in that second ESP. Then move boot,esp flags back to first ESP, and run `sudo update-grub. Grub does not care that second FAT32 is not ESP, but does find the boot files. Or you can manually add boot stanza to 40_custom. https://ubuntuforums.org/showthread.php?t=2478842 & http://askubuntu.com/questions/653101/boot-repair-windows-not-listed But only one ESP per drive is allowed with most systems.

Elon Musk

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

EN: Grub and 2x windows on 1 gpt drive (uefi)

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