I tried to install Windows 8 Developer Preview (x64) on my Macbook Pro 2010.
It turns out Win8 refuses to install on a
MBR
partitioned drive on an
EFI system.
All my drives are
GPT partitioned, so I wondered
what went wrong. It turns out, Win8 is correct about the MBR not being a protective MBR (PMBR):
znek@zoidberg:(~)$ sudo gpt -r show -l /dev/rdisk0
gpt show: /dev/rdisk0: Suspicious MBR at sector 0
start size index contents
0 1 MBR
1 1 Pri GPT header
2 32 Pri GPT table
34 6
40 409600 1 GPT part - "EFI System Partition"
409640 499446368 2 GPT part - "nZoidberg"
499856008 262151
500118159 32 Sec GPT table
500118191 1 Sec GPT header
znek@zoidberg:(~)$ sudo fdisk /dev/rdisk0
Disk: /dev/rdisk0 geometry: 31130/255/63 [500118192 sectors]
Signature: 0xAA55
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
------------------------------------------------------------------------
1: EE 1023 254 63 - 1023 254 63 [ 1 - 409639] <Unknown ID>
*2: AF 1023 254 63 - 1023 254 63 [ 409640 - 499446368] HFS+
3: 00 0 0 0 - 0 0 0 [ 0 - 0] unused
4: 00 0 0 0 - 0 0 0 [ 0 - 0] unused
If you need to recover the PMBR, you can either modify the MBR partition
table to have only the first entry and cover the entire disk or create
a blank GPT partitioned disk image with
Disk Utility and grab
its vanilla PMBR doing this:
znek@zoidberg:(~)$ sudo dd if=/dev/rdisk1 of=pmbr.bin bs=512 count=1
In order to write to /dev/rdisk0, you'll have to unmount all its filesystems…
which is problematic, if that's your boot drive (you'll have to boot from
another drive then). If /dev/rdisk0 isn't busy anymore, then putting the PMBR
in place is trivial:
znek@zoidberg:(~)$ sudo dd if=pmbr.bin of=/dev/rdisk0 bs=512 count=1
Now, gpt won't complain about a suspicious MBR any longer and properly
identify the MBR as being a PMBR:
znek@zoidberg:(~)$ sudo gpt -r show -l /dev/rdisk0
start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
…
