Partition saving should handle converting MBR partitions to GPT

[prestist]

Feature Request

Desired Feature

Now that partition saving bails when its not able to save partitions that are found on a MBR device, we need to have a way to convert the listed save partitions that are MBR partitions to GPT partitions and save them.

Other Information

This request is expecting issue 816 to be resolved first.

[prestist]

Ok, I am currently in the midst of looking into how to convert MBR partition entries into GPT entries, though I have already ran into a question. It looks like GPT has a field called Partition type GUIDs which you can read about here. To my eyes I dont see anything that would indicate a similar concept in MBR.

What should I do about these special GUIDS?
Should I set it as "00000000-0000-0000-0000-000000000000" and let the OS or another app interrogate the saved partitions?
OR should I try for a best effort and handle a few common cases?(I say this with less understanding that I would need to do this atm)

[bgilbert]

MBR has partition type codes, which are a single byte. Most of the possible codes aren't relevant to us, and all of the relevant ones should have corresponding GPT type GUIDs. If we see a type code we don't recognize, I think we should just convert it to a suitable fallback GPT type GUID. AFAIK Linux ignores the type codes/GUIDs anyway, and CoreOS doesn't support dual-booting, so it should be fine to treat the type code conversion as best-effort.