On 15 March 2016 at 19:03, joshua stein <j...@openbsd.org> wrote: > On Sun, 13 Mar 2016 at 01:49:19 -0500, Kenneth Westerback wrote: >> The non-support for Hybrid MBRs was a deliberate choice and there are >> no plans to open that can of worms. Hybrid MBRs are not part of the >> GPT/UEFI standard as far as I can discover, and almost everything >> Google turns up on the intertubes says DON'T DO IT!! > > Well it was certainly not by choice, and any disk with a hybrid MBR > like this could present a problem when installing to it because of > our GPT/MBR heuristics. I'm not asking for hybrid MBR support, but > rather to just choose to use the GPT data when there is a valid GPT > label and at least one EE partition (regardless of size or partition > count), ignoring the rest of the hybrid MBR data entirely. Since we > have proper GPT support, we shouldn't ever need to muck with the MBR > partitions of a disk with a hybrid MBR. >
The counter argument is that a protective MBR *is* defined as being part of a proper GPT formatted disk. And a protective MBR is clearly defined as having 1 and only 1 partition, and that being an EE covering the whole disk. So we are being very conservative and sticking close to the standard as we move into the GPT world. If lack of Hybrid MBR support of any kind continues to bug people I'm sure it will be revisited once we get comfortable with GPT. >> Not being a Mac OS X Disk Utility guru I can't say for sure but I can >> read some of the docs as saying the Hybrid MBR is only created when >> you create a DOS FAT partition. So my first suggestion would be to try >> creating the new partition as something else like HFS+ and changing it >> to A6 with GPT editing during install. > > I tested that on a USB disk and it does appear to create one big > EE/protective partition when everything is HFS+, so I've updated my > MacBook dual-boot guide to recommend that instead of MSDOS. > Cool. Good to know. .... Ken
