Lenovo BIOS boot fix

[Allan Jude]

On 2015-07-13 13:19, Adrian Chadd wrote:
> I'm really confused. Why is the active flag not set again?
>
> I thought that was the whole point of the active flag in the partition table.
>
>
> -a
>

Not that it counts much, but windows does not set the active flag in its 
pMBR.

I was under the impression the standard says that it should not be set, 
as anything actually examining the pMBR as if it were an MBR, obviously 
doesn't support GPT.

I've heard reports that GPT partitions with the active flag set, will 
not boot properly under UEFI.

At this point, I am not sure whether it should be set or not.

This fix is for the Lenovo's with the broken BIOS. It moves the 0xee 
partition in the pMBR to the 2nd slot instead of the first. This does 
not seem to break any previously working hardware, and it makes the 
Lenovo's work.

I have a patch: https://reviews.freebsd.org/D3065
that adds an option to gpart create to a pMBR with this fix applied.

If this gets committed, I can add 'GPT + Lenovo Fix' as an option during 
the installer. I already plan to add 'GPT + Active' for people like 
Colin Percival, who have a Dell or HP that seems to complain if the 
active flag is missing.

Windows avoids these issues by entirely refusing to boot from a GPT 
partitioned disk without UEFI, even though there is no such requirement.


-- 
Allan Jude