Replacing a "legacy" boot computer with a UEFI PC

JeremyBoden · 11-04-2014, 09:54 AM

I'm replacing my 8 year old PC - and I don't understand this GPT/UEFI stuff!
I'd like to keep MBR on my new PC - is this possible?
It has a ASUS® M5A97 LE R2.0 motherboard...

I want to keep my /home partition unchanged - although I'm prepared to reinstall my OS (LMDE) as all the hardware will be changed.

Any help - especially on how to alter the BIOS would be much appreciated.

smallpond · 11-04-2014, 10:13 AM

If your disk is larger than 2 TB or is 4KN format then you need to use a GPT disk label. If it is smaller and uses 512 or 512e (ugh!) format then you can stay with msdos. This is partly independent of whether you boot using BIOS or EFI. Also, most EFI systems have a compatibility mode to support legacy option ROMs or a BIOS bootloader. BIOS is dying. It's a good time to switch.

JeremyBoden · 11-04-2014, 10:50 AM

The disk is only(!) 1TB - however the hardware cluster size is 4KB - but the "logical cluster size" is only 512 bytes. My partitions are positioned at 4KB boundaries (for efficiency).

So the old system didn't need to mess with GPT (the last BIOS update claims to be in 2006).

I suppose I can reluctantly go for this EFI thing - I can take a full file level backup of my disk.

Must remember to disable the Windows only "secure boot" thing.

yancek · 11-04-2014, 11:07 AM

I don't use LMDE so I'm not sure about it but you should have an option when installing to use UEFI/GPT or an MBR install. You can use GPT partitioning with a standard MBR install which requires creating a separate BIOS boot partition. Might check the LMDE site for info.

JeremyBoden · 11-04-2014, 12:04 PM

LMDE is currently Debian(stable+test) + Cinnamon(Mint).
I'll investigate further in the Mint forums.

Am I correct in saying that conversion of a MBR disk to GPT requires deletion of all DOS partitions and consequent loss of all data?

Do additional (non-bootable) 1TB disks need to be converted to GPT/UEFI mode?
Are there problems in booting from MBR sources such as DVD or USB?

bstaletic · 11-04-2014, 03:09 PM

If you enable in BIOS booting both UEFI and legacy booting removable media won't be a problem.

As for installing, UEFI needs efi boot partition. That is actually FAT32 boot partition with ef00 partition type, and using a GPT partition table. I can't provide further information regarding LMDE as I use arch.

I'm not completely sure, but I think gdisk can convert from MBR to GPT without data loss. For making GPT partitions you need to use compatible tools (for example gdisk instead of fdisk).

yancek · 11-04-2014, 04:29 PM

You can use GPT with BIOS or non EFI, see the Grub Manual page below:

https://www.gnu.org/software/grub/ma...tallation.html

Quote:

Am I correct in saying that conversion of a MBR disk to GPT requires deletion of all DOS partitions and consequent loss of all data?

The post below here at LQ might help to answer that.

http://www.linuxquestions.org/questi...ss-4175498257/

Quote:

Are there problems in booting from MBR sources such as DVD or USB?

Booting from a DVD or usb drive is controlled by the BIOS setting and does not have anything to do with your hard disk partitioning method.

JeremyBoden · 11-05-2014, 06:47 AM

That last link is especially useful.
I'm just going to have to wait until the PC arrives and fight with the setup program (AKA the BIOS).

I'll report back...

sgosnell · 11-05-2014, 08:45 AM

You can convert an MBR to GPT without loss of data. Read http://www.rodsbooks.com/ and install gptdisk. Read everything there again, then read this website and you should be able to get your new computer working. As smallpond said, BIOS and MBR are dying, and you'll have to learn UEFI sooner or later, so it might as well be sooner.

JeremyBoden · 11-05-2014, 03:34 PM

I will (reluctantly) do this.
For only one OS and disks with 4K cluster sizes (and smaller than 16TB), MBR works just fine.

If I need lots of resizeable partitions, LVM is a much better way to go than using GPT/UEFI.