Is it ok to switch from BIOS to UEFI boot?

[Derek_]

Hiya!

 

I had to create my USB manually (drag'n'drop, use batch file to make bootable). Being a noob, i didn't really think about BIOS vs UEFI. I booted the USB and started playing around a bit, and i've setup my UPS and done some basic configuration and i remembered the UEFI thing all of a sudden. It didn't even occur to me i was booting via BIOS rather than UEFI but of course i was. I changed the mobo to UEFI and it wouldn't boot.

 

So i looked it up and i found a thread that talked about the directory being called EFI- by default, and to rename it. So i did that. Everything booted ok. And it seems normal. No ill-effects (note it's quite early in my configuration, i don't even have an array configured yet).

 

The real question is: Is it perfectly safe to change the boot mode from BIOS to UEFI after you've made and starting configuring your unRAID? What nuance or caveats could one expect?

 

Cheers

 

p.s. i decided to do the switch because i saw somewhere that if i want to do VM passthrough stuff that i should be using UEFI. Is that right? Whether right or wrong - are there benefits to one over the other?

 

Cheers x2

 

[Frank1940]

2 hours ago, Derek_ said:

The real question is: Is it perfectly safe to change the boot mode from BIOS to UEFI after you've made and starting configuring your unRAID?

Yes.  With a slight qualifier, I have not heard of anyone having an issue to date and it has been several years now since UEFI booting was introduced.  Usually, any problems that were encountered had to do with getting the BIOS configured properly so that the boot actually occurred.  (Most of this is in the past as UEFI BIOS's have evolved.)  As I recall the option was added to Unraid because there were a few MB's being introduced back then that could only boot via UEFI.  Plus, there are folks who have upgrade their MB's and made the switch to UEFI during the upgrade without any issues. 

[John_M]

4 hours ago, Derek_ said:

p.s. i decided to do the switch because i saw somewhere that if i want to do VM passthrough stuff that i should be using UEFI. Is that right? Whether right or wrong - are there benefits to one over the other?

I believe it's the other way round. Difficult hardware is easier to pass though to VMs if you use legacy boot for Unraid but UEFI boot (ie. OVMF instead of SeaBIOS) for the VM. But then, there are plenty of people who understand VMs better than me.

 

One thing you do lose, if you UEFI boot Unraid, is the ability to run MemTest from the boot menu. UEFI boot seems to get stuck waiting for a keyboard if none is connected. All my hardware allows either mode but I have standardised on using BIOS boot.

[Hoopster]

7 hours ago, Derek_ said:

The real question is: Is it perfectly safe to change the boot mode from BIOS to UEFI after you've made and starting configuring your unRAID?

Yes, in fact I was forced to do it to get my system to boot properly. 

 

After a particular unRAID update (6.5.0, I believe) my unRAID server which had been running for a couple of years in BIOS/Legacy boot mode, refused to properly boot.  It just hung at ...loading bzroot and would go no further.  I found that switching to UEFI boot mode (changing the primary boot device to "UEFI:{name of flash drive}" in the BIOS and renaming the EFI- folder to EFI) allowed the system to boot properly.  There had been no hardware changes or unRAID configuration changes on my system, but, with a new Linux kernel and other changes in that release, it would no longer boot in legacy mode.

 

I was not passing though any hardware to my test VMs so I do not know how that may have been impacted by the change from legacy to UEFI boot mode, but, that change was necessary in my case.

[testdasi]

8 hours ago, Derek_ said:

The real question is: Is it perfectly safe to change the boot mode from BIOS to UEFI after you've made and starting configuring your unRAID? What nuance or caveats could one expect?

 

p.s. i decided to do the switch because i saw somewhere that if i want to do VM passthrough stuff that i should be using UEFI. Is that right? Whether right or wrong - are there benefits to one over the other?

 

"perfectly safe"? definitely not.

just "safe"? probably.

 

Anyone having problems passing through PCIe to a VM should be booting in legacy mode.

This has proven to help for both error 43 (Nvidia driver detecting non-Quadro card being used in a VM) and reset issues (e.g. my old R9 390 a long time ago).

Note: "help", not "solve".

 

The only exception is of course if your hardware for whatever reasons requires UEFI to boot. However, it usually is because of a certain specific card requiring UEFI (i.e. a rather unusual circumstance).

So if your hardware is in the nothing-special category but you can't boot in legacy (or suddenly unable to boot in legacy), it's more likely than not that you just need to rebuild your USB stick.

 

There is really no benefit of booting UEFI over Legacy (or vice versa).

So if you have switched to UEFI and nothing seems to stop working then just stick with UEFI.

Just keep it in mind that IF you have issues with passing through PCIe devices in the future, start your troubleshooting with switching back to booting in Legacy Mode.

[Derek_]

My hardware is fairly old, Intel i7-3770, so maybe I should stick with BIOS then. The motherboard is a budget AsRock Extreme4. It only ever had I think two firmware updates, so it wasn't a highly supported board.

 

UEFI was still fairly new at the time - certainly comparitively so.

 

Thanks, I'll switch back to BIOS. Maybe on some future hardware I buy in 3-4 years time I'll re-examine.

 

[nate.smith317]

OMG Thank you @Derek_  I struggled with this for hours on a semi-newer Asus board!  Rename the EFI- to EFI and bam, works.  Bios options can be so dumb, allow conflicting choices, as was my case...  Rename nailed it, thanks again!