I've got a bit of a quirky setup with four drives in my computer. One drive has Windows 11 installed, another has Windows 10, a third is just for storage, and the last one is running Arch Linux. I'm planning to ditch Windows 10 and install CachyOS on that drive. However, I want to keep Windows 11 available for work until I can fully migrate my stuff over. Here's the kicker: the Windows 11 installation didn't create its own EFI partition; instead, it used the existing one from Windows 10. I'm worried that if I format the Windows 10 drive, it could mess up my ability to boot into Windows 11. I came across some advice suggesting I unplug other drives and create a new EFI partition, but that sounds like a hassle just to keep Windows 11 running. Luckily, I've got GRUB set up on my Arch drive, which can boot into Windows 11. So, my question is: can I format the Windows 10 drive (along with its EFI partition) and still boot into Windows 11 via GRUB on my Arch drive? Or is that Windows EFI partition essential for some reason? I'm also hesitant to leave that EFI partition on the Windows 10 drive because I feel like it could complicate the CachyOS installation, though maybe I'm being overly cautious.
3 Answers
You'll definitely need the Windows bootloader since GRUB chainloads it to boot into Windows. A solution could be to clone the partition temporarily, but keep in mind that managing bootloaders can get tricky. It's better to have a clear setup than run into booting issues later.
Get ready to dive in and back everything up! I'd recommend moving the Windows 11 partition about 500MB over, using bcdedit to recreate the Windows bootloader on the right drive. Once you confirm it works, you can wipe the old drive. I run multiple OSs off one drive, so I only have one EFI, and it hasn’t caused any issues for me, but unplugging other drives during a new install can save headaches.
While this leans toward a Windows question, my experience shows that Windows usually installs itself on the specified drive. You could temporarily remove the boot flag from the EFI partitions to help the Linux installers. But since you’ve already got Windows 11 set up using that other drive's EFI, it might be too late for that. I’d recommend checking Windows forums for more info about EFI partitions, but you might be fine keeping the EFI partition on the Linux drive as is.
After doing some more reading, it seems like leaving that EFI partition on the Linux drive could work. I might just format everything for Linux and hold off on touching that partition until I’m ready to remove Windows. Alternatively, I could consider just keeping the Windows 10 drive intact instead.
Ah man, that's a real hassle! I don't want to mess things up if I can avoid it.