[parted-devel] [PATCH 0/4] Add ability to set GPT PMBR boot flag

[Phillip Susi]

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On 1/27/2012 7:59 PM, bcl at redhat.com wrote:
> Some BIOS systems refuse to boot from GPT disks unless the boot
> flag of the PMBR has been set. Matthew Garrett has written a patch
> to add a disk_set command and a legacy_boot flag for the disk. I
> have added display of the disk flags using a new output line, like
> so:

I wonder if this wouldn't be better solved in a more generic way.
This seems to be a specific case of a more general problem: two
different partition tables are actually on the disk, and one ( gpt )
supersedes the other ( dos ), and there is no way to go back to
manipulating the dos partition table underneath gpt.

Maybe what is needed is a switch to force a specific partition table
so you can run parted and ignore the gpt parts and manipulate the disk
as if it were just a plain dos partition table.  Then you could use
the conventional methods to set a boot flag on a partition in the MBR
( maybe the protective 0xEE partition ), or maybe add multiple
partitions to end up with a hybrid GPT/MBR partition table that still
exposes some parts of the disk to non GPT aware operating systems.

Or maybe gpt should become hybrid aware and grow partition flags that
designate a gpt partition that should be exposed in the PMBR.  Then it
could support the legacy_boot flag as a partition flag that would
cause it to set the boot flag in the PMBR, either on the protective
0xEE partition, or on the exposed legacy partition.

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