New to UEFI: Dual Boot Arch & Windows 8.1 on Separate Drives [SOLVED]

egan · 2014-12-09 02:27:16

So I've been using Arch for years and have installed dozens of times on BIOS/MBR systems.
I just built a new desktop and I am completely lost on how to deal with the UEFI... everything is so different.

I have 3 drives. In order:

1. sda: SSD for Arch root.
2. sdb: SSD for Windows.
3. sdc: HDD for Arch home.

I primarily use Arch, and I envision the Arch SSD being first in the boot order, with the bootloader chain-loading Windows when I wish to boot it.

I made a 512MiB FAT32 partition on sda1 using GParted, setting the "boot" flag on it. I would have done it from within the installer but I am unfamiliar with GPT-compatible disk utilities and the wiki doesn't have too much of an explanation.
I then proceeded to install Arch, mounting the ESP at /boot as suggested in the guide.
Autocreated grub config at /boot/grub/grub.cfg, which only detected Arch.
I tried to set up a chain load to Windows by editing /etc/grub.d/40_custom as described here:
https://wiki.archlinux.org/index.php/GR … menu_entry

The result is that Arch does not boot at all. Windows still boots fine, as expected since nothing changed.

So how exactly does one go about setting up Arch to boot from its own GPT drive?
It seems weird to me that the linux kernel images would be stored on the tiny ESP.
And how would I modify the bootloader to chainload Windows on its own GPT drive, with its own ESP?

I'm used to GRUB so that's what I've tried, but if there is a much easier option I'm open to it.
I'd really appreciate any help, it's been quite frustrating.

Last edited by egan (2014-12-09 03:38:24)

egan · 2014-12-09 03:38:04

Okay, well as usually happens, when I resort to help I end up solving my own problem.
In this case however, I still don't have a good grasp of what is going on.

I deleted the partition table with sgdisk --zap-all /dev/sda and then used gdisk to recreate it, specifically setting the code for /dev/sda1 to ef00.
I then reformatted the FAT partition, leaving the other one alone. After mounting /dev/sda1 to /boot and reinstalling linux and grub, I ran:

grub-install --target=x86_64-efi --efi-directory=$esp --bootloader-id=arch_grub --recheck

as described in the wiki, and

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

And it worked, including automatically detecting Windows on the other drive. Not sure what went wrong the first time but I'm glad to get it working.

Last edited by egan (2014-12-09 19:46:58)

Head_on_a_Stick · 2014-12-09 15:23:07

egan wrote:

Not sure what went wrong the first time

egan wrote:

setting the "boot" flag on it

^ That -- use gdisk next time and just create the ESP as type "ef00": no flags required (the partition type tells your firmware that it's an ESP).

Arch Linux

#1 2014-12-09 02:27:16

New to UEFI: Dual Boot Arch & Windows 8.1 on Separate Drives [SOLVED]

#2 2014-12-09 03:38:04

Re: New to UEFI: Dual Boot Arch & Windows 8.1 on Separate Drives [SOLVED]

#3 2014-12-09 15:23:07

Re: New to UEFI: Dual Boot Arch & Windows 8.1 on Separate Drives [SOLVED]

Board footer