Wed 02 Dec 2009 11:06:54 AM UTC, original submission:
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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