Should I remove Grub from the MBR when using EFI system?

Guytas

1/8/23, 12:27 AM

Not sure why boot-info reports this:

=> Grub2 (v1.99-2.00) is installed in the MBR of /dev/sda and looks at sector 
    2048 of the same hard drive for core.img, but core.img can not be found at 
    this location.

I have an iMac dual-boot with Windows10 and Ubuntu 21.04. The disk is in EFI mode. I've just succeeded having both OS to start with the Grub. But Windows is somehow very sensitive to the MBR. If the MBR contains partitions, Windows refuses to boot.

I suspect that because of the above message. I cannot touch the partitions with Disk because it updates the MBR and Windows does not start any more. To fix it, I have to use gdisk to set the Protective MBR. After that, Windows can start.

Should I remove the Grub from the MBR? If so, how can I do that?

1 + 5

grub2

dual-boot

Nmath

1/8/23, 12:33 AM

Your question has a simple answer, but answering this question probably doesn't solve your actual problem. You should always ask about the actual problem that you face and provide details and context about that problem. Otherwise, if you ask about a proposed solution and that solution doesn't help you, you're no better off and may even end up in a worse situation than you started. This is known as an [XY Problem](https://meta.stackexchange.com/a/66378).

Nmath

1/8/23, 12:34 AM

I suspect that you have installed a mix of MBR and UEFI OS installations. You will need to be consistent with your use of MBR/legacy **or** UEFI. Don't mix and match. You may need to reinstall one or more operating systems.

guiverc

1/8/23, 12:45 AM

The MBR (*Master Boot Record*) is the first 512 bytes of a disk; it's been reserved since the 1980s for that feature (made a standard with the original IBM PC of 1981 had hard drives available for it). You say "*If the MBR contains partitions*" but you cannot fit partition(s) in 512 bytes of disk space; your question doesn't make sense. uEFI replaced MBR yes, but the first 512 bytes of a disk is still reserved for that purpose (GPT or *legacy* partition tables).

Guytas

1/9/23, 12:03 AM

ok, I'm confused then... Because when I run gdisk, goes in expert mode, then hit o, it is saying MBR disk identifier: 0x0000000000, then MBR partitions: Then it lists the partitions. That is the partitions I was referring to. I understand that this sector is only 512 bytes but what ever that is, is causing Windows not to start if it does contains partitions (the way gdisk called it). You're right Nmath, I should have ask the right question. I'll rephrase my question for: "How to prevent DISK from changing MBR to an Hybrid MBR" Please track it!

guiverc

1/9/23, 12:09 AM

MBR technically refers to the *Master Boot Record* which is the first 512 bytes of non-floppy disk drives since ~1982 (standard set by IBM PCs & PC-DOS 2.0). The original partition layout did **not** have a formal name, I've referred to it as *legacy*, but it can also be called MSDOS, or MBR which can be confusing as there is no actual correct name. If using the MBR/DOS you need to be clear you mean partition table (ie. MBR partition table) as MBR means something different. The MBR disk identifier clarified it wasn't talking about an actual MBR as there is no identifier; its the first sector

Score:1

Ubuntu

Nmath

1/8/23, 12:29 AM

GRUB is needed to boot Ubuntu. Without it, you won't be able to boot Ubuntu.

Don't remove it.

0 + 0

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Should I remove Grub from the MBR when using EFI system?

TH: ฉันควรลบ Grub ออกจาก MBR เมื่อใช้ระบบ EFI หรือไม่

RO: Ar trebui să elimin Grub din MBR când folosesc sistemul EFI?

RU: Должен ли я удалить Grub из MBR при использовании системы EFI?

VI: Tôi có nên xóa Grub khỏi MBR khi sử dụng hệ thống EFI không?

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