Arch Linux

cap

Member

Registered: 2015-10-14

Posts: 5

boot efi bootloader from grub installed in MBR

Hi,

for the longest time I have been successfully using a win/Arch dualboot system with grub2 and an MBR boot loader.
Now. I was able to get my hands on an SSD so I installed Windows to get the ball rolling.

When I choose the SSD as first boot drive in BIOS, booting into the new Win install works without any issues.
Unfortunately, I don't have time to migrate my linux system to the SSD right away.

Is it possible to include the EFI bootloader on the SSD into my grub on the old drive, so I don't have to switch boot drives in BIOS?

Using

grub-mkconfig -o /boot/grub/grub.cfg

does not detect the new windows install.
I have tried adding a manual entry in /etc/grub.d/40_custom, but I get an "invalid signature" error

These are the entries I tested  - none of them working

menuentry "Windows SSD1" {
                insmod part_gpt
                insmod fat
                insmod chain
                search --no-floppy --fs-uuid --set=root --fs-uuid 7827-18B2
                chainloader /EFI/Microsoft/Boot/bootmgfw.efi
        }

menuentry "Win SSD2" {
   insmod fat
   set root=(hd4,gpt2)
   chainloader (${root})/EFI/Microsoft/Boot/bootmgfw.efi
   boot
}

Is it actually possible to do this, or what would be the best way to do this?

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 9,003

Website

Re: boot efi bootloader from grub installed in MBR

Is it actually possible to do this

No, it is not possible to chainload a UEFI system from a non-UEFI bootloader.

---

Jin, Jîyan, Azadî

cap

Member

Registered: 2015-10-14

Posts: 5

Re: boot efi bootloader from grub installed in MBR

I was afraid of that.

How could I best fix this? Is it possible the other way round?
Or could the MBR bootloader point to another grub install that is installed as UEFI boot loader?

loqs

Member

Registered: 2014-03-06

Posts: 19,101

Re: boot efi bootloader from grub installed in MBR

Or could the MBR bootloader point to another grub install that is installed as UEFI boot loader?

No once the system is started in CSM / BIOS mode UEFI functionality is not available.
Why not install an EFI based bootloader on the ESP that can boot either OS?

Last edited by loqs (2019-08-04 19:54:18)

cap

Member

Registered: 2015-10-14

Posts: 5

Re: boot efi bootloader from grub installed in MBR

Why not install an EFI based bootloader on the ESP that can boot either OS?

Fair enough, will do. Thanks!