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

[Carsten Dumke]

URL:
  <http://savannah.gnu.org/bugs/?28149>

                 Summary: add support for hybrid MBR/GPT to grub2
                 Project: GNU GRUB
            Submitted by: cdumke
            Submitted on: Mi 02 Dez 2009 12:06:54 CET
                Category: Disk &amp; Partition
                Severity: Major
                Priority: 5 - Normal
              Item Group: Feature Request
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: Carsten Dumke
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 
                 Release: 1.97
         Reproducibility: None
         Planned Release: None

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Details:

Hello,

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,

Carsten

[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





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File Attachments:


-------------------------------------------------------
Date: Mi 02 Dez 2009 12:06:55 CET  Name: grub2-hybrid-mbr-gpt-detect.patch 
Size: 803B   By: cdumke
patch to detect GPT in hybrid MBR
<http://savannah.gnu.org/bugs/download.php?file_id=19183>

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