PC won't boot into UEFI Arch after temporarily swapping Hard Drive

Emmescingue · 2021-10-03 15:33:25

Hi, I've recently had to reinstall Arch, but this time I chose to do so on a new hard drive, using the UEFI/GPT method.

For as much as that new way of doing things confuses me, I had managed it in the past, even with a dual boot on a laptop. This time, being just a standalone install, it was even easier.

Everything worked yesterday, and I could boot into the install after having removed the USB with the live medium. But now, even though I select the right hard drive (I've tried physically unplugging all others, I still only boot into EFI shell), even though I've tried disabling Legacy boot modes from the motherboard's "BIOS" (not even sure what to call it now), even though I've booted back into the live medium and saw with my eyes that the EFI System Partition was there and GRUB was still installed, there just is no way that I can find of letting my PC know to boot into Arch. Boots into Windows, also through UEFI, just fine.

Thing is, nothing changed between yesterday and today. NOTHING CHANGED. Except, of course, for this: Since for now I don't have enough SATA cables, to swap between Windows 10 on my SSD and Arch on my HDD, I simply power off, unplug from one, plug in the other. Windows never complained about this, however the first time I did this, after of course having confirmed that the Arch install had worked, upon swapping back this issue appeared. I couldn't possibly have broken something in the Arch disk, because it was flippin' unplugged.

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I suppose my problem is that I'm ignorant in UEFI, but dear God, I just can't find an explanation of how exactly this is different from BIOS in an operational sense, anywhere. I've read the Arch Wiki pages, looked up on Google, can't find a source that will explain to me what exactly the differences are operationally. How do I do in UEFI the things that I could do in BIOS, like change the bloody boot disk? I don't even understand where the difference between UEFI and BIOS actually resides, my motherboard seems to have both?? So when is it exactly that I go from one to the other? Does the boot disk selection happen before the choice between UEFI and BIOS is made? Figure this, in the EFI shell, I can't even read the output of "help" because the screen will scroll and I have no way of reading half the things. What is the EFI shell even for???

So please, if you have any intelligible documentation, I'd immensely appreciate if you could share it.

You have my permission to insult me for my vent, also sorry if something else about my topic is bad, this is the first time I am desperate enough that I resort to asking you guys (I've managed for more than three years, but here, I'm just baffled at how random this issue is), and I need to learn to do this I suppose, so feel free to tell me how I'm a bad forumer, that will help us all in the future. You don't even have to be polite about it, I don't mind.

V1del · 2021-10-03 15:45:48

That's normal and expected for the vast majority of UEFI implementations. When you remove a drive, the associated NVRAM entries identifying the binary to boot will get forgotten. In the case of GRUB you'll need to rerun the appropriate grub-install command to regenerate the NVRAM entry. If you want to be able to remove your drives install the bootloader you intend to use into the fallback location, see: https://wiki.archlinux.org/title/Unifie … nced_drive

For the inner working question, Maybe read more of the UEFI article linked earlier. The main point for a linux user/potential dual booter for UEFI is that it actually inherently allows multiple bootable entries on the ESP. In practice this means for example if you are dual booting that you actually can boot Windows and Linux without worrying about Windows overriding the boot loader. On a normal BIOS system the bootloader resides in the first few bytes of the beginning of the hard disk and can and will be overwritten by multiple operating systems. on UEFI systems the UEFI checks and references bootable binaries on the ESP where there can be multiple of. Another thing is that you can use secure boot to ensure a secure boot chain so that a potential attacker can't trivially boot their own software. I personally think this blog post describes the underlying concept and differences pretty well.

Emmescingue · 2021-10-03 16:19:42

Thank you V1del, you've been quite literally illuminating. Couldn't have asked for a better answer.

When and how should I mark my question as resolved? Is changing the title to [Solved] all there is to it?

progandy · 2021-10-03 16:20:24

Yes, edit the title of the first post.

As for long output in the EFI shell, most likely you can scroll with PgUp/PgDown. Maybe also press a modifier like Shift, Ctrl or Alt.

Last edited by progandy (2021-10-03 16:20:53)

Emmescingue · 2021-10-03 16:30:08

Thank you progandy, I've tried PgUp/PgDown, but not in combination with the modifiers, I'll try that.

I think I'll change the title once I've actually moved GRUB to the fallback directory and managed to boot across swaps, just in case some other shenanigans pop up.

Finally, I'd like to apologize for this: had I read the Wiki more attentively, I would have found that voice on removing hard drives, and I could have kept the streak of not posting going for a while longer. Just wish it were a bit more glaring, I completely missed it. Hopefully though this post might help someone find this more easily in the future.

I thank you guys kindly once again for your time.

Arch Linux

#1 2021-10-03 15:33:25

PC won't boot into UEFI Arch after temporarily swapping Hard Drive

#2 2021-10-03 15:45:48

Re: PC won't boot into UEFI Arch after temporarily swapping Hard Drive

#3 2021-10-03 16:19:42

Re: PC won't boot into UEFI Arch after temporarily swapping Hard Drive

#4 2021-10-03 16:20:24

Re: PC won't boot into UEFI Arch after temporarily swapping Hard Drive

#5 2021-10-03 16:30:08

Re: PC won't boot into UEFI Arch after temporarily swapping Hard Drive

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