Arch Linux

GlennZ

Member

Registered: 2020-08-24

Posts: 2

[SOLVED] GRUB Chainloading 2 EFIs for dualboot with Win10

Hi all,

pardon me if this is an already common newbie issue but I've tried reading a bunch of threads here and still I can't seem to find a solution that suits me.

I've installed Arch along side Windows 10 on my desktop PC, I did an extra EFI partition on the same disk though. I know it's not good practice but this gives me the feeling that I'm not compromising my Win installation in any way while I mess around with Arch.
Usually other distros (Ubuntu, Manjaro) with a scripted installer just figure out this situation by themselves, adding an entry for Win on grub, so I can just point my machine to boot from the "grub" EFI partition and then choose the OS. If the shit hits the fan I can always re-point my PC to boot from the other (Win) EFI partition and it's all good.

In this Arch installation I've used this command to install grub:

 grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=GRUB --removable 

At the moment though, GRUB doesn't list Windows at all.

At some point I've tried mounting the other EFI and run os-prober and then grub-mkconfig again. It looked like os-prober found the Win EFI but still, no entry in GRUB.

Can you please help me? How do I chainload the other EFI partition into GRUB? Can you point me to any relevant wiki article? I'm getting lost.

Thank you.

Last edited by GlennZ (2020-08-24 15:12:16)

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 9,003

Website

Re: [SOLVED] GRUB Chainloading 2 EFIs for dualboot with Win10

How do I chainload the other EFI partition into GRUB?

Create a file at /boot/grub/custom.cfg with this content:

menuentry 'Windows 10' {
   search --fs-uuid $uuid --set=root
   chainloader /EFI/Microsoft/Boot/bootmgfw.efi
}

Replace $uuid with the actual UUID of the Windows EFI system partition.

---

Jin, Jîyan, Azadî

GlennZ

Member

Registered: 2020-08-24

Posts: 2

Re: [SOLVED] GRUB Chainloading 2 EFIs for dualboot with Win10

Well Sir, I have no idea of the reasoning process behind this but it worked like a charm.

Thanks!