[Parted-maintainers] Bug#441033: parted does not undestand GPT/MBR hybrid

[Osamu Aoki]

found 441033 1.8.8.git.2008.03.24-11
retitle 441033 parted breaks GPT/MBR hybrid system (Intel Mac)
thanks

Hi,

When updating GPT partition table, parted assumes system is pure EFI
booted with GUID partition table (GPT).  This is not the case for Intel
Mac or other newer MOBO if the user wishes to use BIOS emulation.

parted has 2 problems here:
 * It erase first 444=(512-2-64-2) bytes where classic MBR bootloader is
   installed. --> It should preserve it (at least when hybrid partition
   is found)
 * It erases partition data for /dev/sda2, /dev/sda4, and /dev/sda4
   stored in the last part of MBR.  --> It should update it following
   updated GPT data like gptsync does for hybrid partition.

I suggest to add one more mklabel option: something like "gpt-hybrid"

For system with matching initial partition tables between GPT and MBR,
assume it as "gpt-hybrid".  

For system with non-zero byte at the first byte of disk with GPT, ask
user about updating MBR contents if it is not in sync.

For "gpt-hybrid" system, never over write first 444=(512-2-64-2) bytes
and always update last 64+2 bytes by GPT configuration just like gptsync
in refit source package does.  (I guess borrowing it into parted is good
idea.)

For people looking for workaround for debian-installer, see
  http://wiki.debian.org/MacBook/DebianInstallTutorial

As for the original bug reporter's complain that partition type is the
same as windows, it seems it is by design.  As I see 
  http://en.wikipedia.org/wiki/GUID_Partition_Table
under "Partition entries (LBA 2–33)", both OS uses "Partition type GUID"
 EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
Thus no way to distinguish them apart.  If the original reporter does
not like message given by other partitioning tools such as gptsync
reporting it as "EFI System (FAT)", he needs to complain to that
program.  msftres seems to be some macOS thingy though.

Cheers,

Osamu