[Solved] Switching over from BIOS to UEFI

Moonbane · 2014-07-22 10:42:25

Hello,

Since I have decided to upgrade my old system (Q6600), I seem unable to find an answer regarding the switchover.

My old system has - obviously - still a BIOS, my new Mainboard will have UEFI.

I already have a SSD with a working Arch (MBR).

Under a BIOS I'd just disable UUID in /etc/default/grub, put the SSD in the new Computer, boot from arch iso, chroot into it and reinstall grub. Then I'd get my new UUIDs, mount and add the new disks to the fstab and maybe set new hooks for mkinitcpio.

So but now my new Board has UEFI.

1. Will UEFI recognise my current / - partition? Its from MBR (ext4)
2. Would it suffice to set a (new) /boot partition in FAT32 - 512 MiB and flag it as EF00 - as per arch linux wiki?
3. Any further steps required?
4. Is it necessary to install grub / or beneficial?

Thanks for your answers!

Last edited by Moonbane (2014-08-25 10:14:00)

Head_on_a_Stick · 2014-07-22 11:07:02

Hello Moonbane, welcome to Arch
It would probably be simplest to plug in the new SSD then disable EFI-mode from your BIOS settings and enable "CSM" or "Legacy" mode. I could be wrong, but I think you would then just have to change the UUIDs in /etc/fstab & /boot/grub/grub.cfg; re-installing GRUB would not be neccessary.
If your SSD is using MBR (rather than GPT-formatting), then the wiki says:

It is recommended to always use GPT for UEFI boot, as some UEFI firmwares do not allow UEFI-MBR boot.

It may be possible to use gdisk to convert your MBR disk to GPT; I've never tried this...

Moonbane · 2014-07-22 11:48:06

Head_on_a_Stick wrote:

Hello Moonbane, welcome to Arch

I have to admit, that I use arch for 3 years now.... It just ran.

These were my first questions I couldn't answer by researching myself.

So in legacy mode it would behave like a BIOS... nice to know

Thank you.

Head_on_a_Stick · 2014-07-22 12:48:43

Actually, thinking about this the UUID would remain the same (it's the same drive) --- you should be able to just plug in the old drive, enable "Legacy" mode and it should boot up as normal...

surfatwork · 2014-07-22 16:30:45

Yes, the UUIDs wont change. The system should boot up just as normal in Legacy BIOS mode.
Having said that, this may be a good opportunity to reinstall with GPT and UEFI. No longer having to resort to extended partitions and malarkey was a revelation.

srs5694 · 2014-07-25 17:09:05

surfatwork wrote:

this may be a good opportunity to reinstall with GPT and UEFI. No longer having to resort to extended partitions and malarkey was a revelation.

I've been trying to help a partitioning newbie deal with a problem involving primary vs. logical partitions on another forum. It's like pulling teeth. I understand it intimately, but trying to explain it to somebody who doesn't makes me realize again just what a pain it is....

Anyhow, as the author of gdisk, I can say that an MBR-to-GPT conversion via gdisk is usually painless and quick. If the final partition bumps up against the end of the disk (with few or no free sectors at the end), it may need to be shrunk slightly. There's also always the possibility of a disaster when doing such a conversion -- although what gdisk does is actually pretty simple, compared to something like resizing an existing partition. (Partition tables are ridiculously simple data structures compared to filesystems!)

Once you understand it, EFI-mode booting is much more sensible than BIOS-mode booting. Most of the problems you read about on the Web are caused by either lack of understanding or buggy EFI implementations. You can correct the first of those with some reading (try my page on EFI-mode Linux installs, Adam Williamson's blog post on how EFI works, and the Arch wiki for starting points), but the second will either be a crap shoot or require careful research before buying hardware to ensure you get something decent.

surfatwork · 2014-07-29 17:44:53

I agre - EFI mode booting is far more logical once you understand it. I have a HP 840G1, and the EFI on this is pretty decent from the booting perspective. It "is" a bit obtuse sometimes, but the core bits work fine.

Moonbane · 2014-08-25 10:17:33

I marked the topic as solved.

1. Yes you can just plug the old Drive in, activate Legacy and Boot. Does only work on fallback-initramfs - mkinitcpio necessary for direct boot.

2. UUIDs stay the same, even my DMRAID worked perfectly.

Thanks for your help

Arch Linux

#1 2014-07-22 10:42:25

[Solved] Switching over from BIOS to UEFI

#2 2014-07-22 11:07:02

Re: [Solved] Switching over from BIOS to UEFI

#3 2014-07-22 11:48:06

Re: [Solved] Switching over from BIOS to UEFI

#4 2014-07-22 12:48:43

Re: [Solved] Switching over from BIOS to UEFI

#5 2014-07-22 16:30:45

Re: [Solved] Switching over from BIOS to UEFI

#6 2014-07-25 17:09:05

Re: [Solved] Switching over from BIOS to UEFI

#7 2014-07-29 17:44:53

Re: [Solved] Switching over from BIOS to UEFI

#8 2014-08-25 10:17:33

Re: [Solved] Switching over from BIOS to UEFI

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