Date: Sun, 10 Jun 2007 21:35:47 +0100 From: Rui Paulo <rpaulo@fnop.net> To: Marcel Moolenaar <xcllnt@mac.com> Cc: freebsd-hackers@freebsd.org, Matthew Dillon <dillon@apollo.backplane.com>, freebsd-current@freebsd.org, Ivan Voras <ivoras@fer.hr>, freebsd-geom@freebsd.org Subject: Re: GPT - (last) call for action Message-ID: <861wgjwnrw.wl%rpaulo@fnop.net> In-Reply-To: <8B01C1EC-D61A-484F-B308-6D6C8EB00EE6@mac.com> References: <f4ek4o$i4u$1@sea.gmane.org> <4AB3C4C0-0DA1-482F-A4CD-375A53332F29@mac.com> <f4f14d$lhe$1@sea.gmane.org> <4D7CDA24-48FE-4319-A320-C8D7165E9EBC@mac.com> <200706092128.l59LSjRs027671@apollo.backplane.com> <57F8CCC1-1841-41AE-9F82-0C87FE53BE99@mac.com> <200706101752.l5AHqdE0035954@apollo.backplane.com> <8B01C1EC-D61A-484F-B308-6D6C8EB00EE6@mac.com>
next in thread | previous in thread | raw e-mail | index | archive | help
At Sun, 10 Jun 2007 11:08:47 -0700,
Marcel Moolenaar wrote:
>
>
> On Jun 10, 2007, at 10:52 AM, Matthew Dillon wrote:
>
> > :Technically speaking, the MBR can only have a single partition of
> > :type 0xEE that covers the whole disk. This is to protect the GPT
> > :from MBR-specific tools that do not know about the GPT. This is
> > :not a bootable slice by definition.
> > :
> > :Practice is different. To support bootcamp on Intel-based Macs,
> > :the MBR will have real partitions that mirror GPT partitions or
> > :otherwise describe partitions outside the GPT controlled area.
> > :These can be bootable partitions and the protective partition
> > :(the one with type 0xEE) will not cover the whole disk anymore.
> > :
> > :The nasty part is keeping MBR and GPT partitions in sync, so it
> > :may be better to have the MBR partition fall outside the GPT
> > :controlled area. This can be done because the GPT header contains
> > :the LBA of the first and last sectors on the disk that can be
> > :assigned to a partition. You can free up space for MBR partitions
> > :after the primary GPT table by adjusting the first LBA. In the
> > :MBR partition you can put a GPT aware boot loader that uses the
> > :GPT to find the real partitions...
> > :
> > :--
> > :Marcel Moolenaar
> >
> > In the bootcamp approach, is the GPT (0xEE) slice the first slice,
> > and the bootcamp slice the second slice? I'm assuming it is. Do
> > they mirror a GPT partition or do they use the uncontrolled area
> > approach?
>
> I seem to recall that the 0xEE partition is not the first, but rather
> the second or third. It would make sense, because it has no function
> other than to have the disk appear used. Bootcamp uses the mirroring
> approach.
No.
The first partition is the EFI GPT (0xee):
% fdisk -1
******* Working on device /dev/ad0 *******
parameters extracted from in-core disklabel are:
cylinders=116280 heads=16 sectors/track=63 (1008 blks/cyl)
Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=116280 heads=16 sectors/track=63 (1008 blks/cyl)
Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 238 (0xee),(EFI GPT)
start 40, size 409600 (200 Meg), flag 0
beg: cyl 0/ head 0/ sector 41;
end: cyl 406/ head 6/ sector 14
% gpt -r show ad0
gpt show: ad0: 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
409640 41943040 2 GPT part - Apple HFS
42352680 74857527 3 GPT part - FreeBSD UFS/UFS2
117210207 32 Sec GPT table
117210239 1 Sec GPT header
--
Rui Paulo
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?861wgjwnrw.wl%rpaulo>