bugGNU GRUB - Bugs: bug #28149, add support for hybrid MBR/GPT to...


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bug #28149: add support for hybrid MBR/GPT to grub2

Submitter:  Carsten Dumke <cdumke>
Submitted:  Wed 02 Dec 2009 11:06:54 AM UTC
Category:  Disk & Partition Severity:  Major
Priority:  5 - Normal Item Group:  Feature Request
Status:  Invalid Privacy:  Public
Assigned to:  None Originator Name:  Carsten Dumke
Open/Closed:  Closed Release:  1.97
Release:  Reproducibility:  None
Planned Release:  None

Wed 02 Dec 2009 03:12:55 PM UTC, comment #2: 

Thank You for the fast reply.

The hybrid MBR was in my case written by parted2 (2.0-current with parted2-gpt-mbr-sync.patch from OpenSuSE 11.x).

Keep up the good work!

Best regards,


Carsten Dumke <cdumke>
Wed 02 Dec 2009 02:43:31 PM UTC, comment #1: 

GRUB2 supports hybrid GPT. It has even a tool gptsync for manipulating MBR of hybrid GPT. However Hybrid GPT has to have protective entry in MBR as its first entry and I see no reason to break this rule, especially that hybrid GPT is just a kludge for legacy systems and often is worse as either GPT or MSDOS. So your partition table is just invalid. Contact the developpers of whatever tool created it and say that protective entry has to be the first one

Vladimir Serbinenko <phcoder>
Project Administrator
Wed 02 Dec 2009 11:06:54 AM UTC, original submission:  


hybrid MBRs are not supported by the UEFI 2.3 standard (see [1]), but nevertheless found in the field (see [2]).
OpenSuSE has added support for syncing GPT-partitions to a hybrid MBR to parted2 (see [3]) and so it would be nice if grub supports such (non-standard) hybrid MBRs.

Hybrid MBRs can have the EFI-GPT labeled partition in any of the 4 slots of the MBR.

A hybrid MBR may look in linux-fdisk like this:
# LANG=C fdisk -l /dev/sda

WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted.

Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

Device Boot Start End Blocks Id System
/dev/sda1 * 1 26 208828 83 Linux
/dev/sda2 27 27 8032 83 Linux
/dev/sda3 28 5222 41726145 83 Linux
/dev/sda4 1 1 0+ ee EFI GPT

Partition table entries are not in disk order
-------- end of output -----------

To implement this feature grub2 should scan all 4 MBR partitions for the EFI GPT-label.

This would also lead to an enhanced user-experience on the side of the end-user (see [4], [5]).

I've attached a patch to implement the detection of GPT for hybrid MBRs.

Best regards,


[1] http://www.uefi.org/specs/
[2] http://www.t13.org/Documents/UploadedDocuments/docs2009/e09150r0-EDD-4_Hybrid_MBR_partition_records_annex.pdf
[3] https://features.opensuse.org/302485
[4] http://lists.gnu.org/archive/html/grub-devel/2009-07/msg00367.html
[5] http://lists.gnu.org/archive/html/grub-devel/2008-09/msg00188.html

Carsten Dumke <cdumke>


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Attached Files
file #19183:  grub2-hybrid-mbr-gpt-detect.patch added by cdumke (803B - application/octet-stream - patch to detect GPT in hybrid MBR)


Depends on the following items: None found

Items that depend on this one: None found


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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2009-12-02 phcoder Open/ClosedOpen Closed
        StatusNone Invalid
    2009-12-02 cdumke Attached File- Added grub2-hybrid-mbr-gpt-detect.patch, #19183

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