change disk from MBR to GPT - GRUB2 reinstall issue

English Install/Boot/Login
1

Hi

I’ve just wasted 2 hours unsuccessfully changing the primary hard disk from MBR to GPT. I couldn’t get GRUB2 reinstalled after the change (which seemed to go OK) so it wouldn’t boot. The drive has 2MB free space at the start but doesn’t have an EFI partition.

I tried the rescue boot on the Leap 42.2 install USB, with chroot & grub2-mkconfig & grub2-install. Both complained that they weren’t going to do it as block chain is unreliable (from memory).

Do I need to create the EFI partition before I can make this work?

What are the correct steps to get it booting again after the MBR-> GPT change?

Thanks
David

p.s. the HDD also has a legacy windows Vista partition on it, but I now only use that within a VM within OS, so it can be ignored for booting purposes.

2

What was the reason to do it?

What are the correct steps to get it booting again after the MBR-> GPT change?

It depends on what you are trying to achieve. So far it sounds like change for the change’s sake.

Are you booting with EFI or legacy BIOS?

3

What is the joy of that?

4

No joy - frustration. Some people say that frustration and failure are good for the character. I think otherwise. :slight_smile:

It was and is BIOS booting. I can change it to UEFI if that’ll help.

I’m trying to make the change preparatory to some consolidation: move to an SSD disk & move some partitions to other disks.

5

I probably miss the clue, but when you have a BIOS system, you boot in legacy mode, you have to boot the installer in legacy mode and your installed system will be in legacy mode. And that BIOS won’t support GTP disks as boot device.

When you have an EFI system, you boot in EFI (and that extra partition is there then already), you boot the installer in EFI mode and your installed system will be EFI. I assume it will still be possible to have an DOS/MBR partitioning with that on the boot disk, but most often it comes with GPT partitioning that then will be understood by the computer firmware.

Please correct me if I am wrong.

6

In this case you need to either create BIOS boot partition (if you want to install grub2 in MBR) or use generic MBR code (which in this case will actually be Syslinux GPTMBR) and install grub2 in partition.

I can change it to UEFI if that’ll help.

If you know how to do it in EFI, that probably will.