booting off GPT partitions

Robert Noland rnoland at
Thu Jan 28 12:06:57 UTC 2010

On Wed, 2010-01-27 at 20:23 -0600, Brooks Davis wrote:
> On Thu, Jan 28, 2010 at 12:27:54AM +0100, Dimitry Andric wrote:
> > On 2010-01-27 22:27, John Baldwin wrote:
> >> GPT was defined along with EFI, so many folks assume that you have to use EFI
> >> to boot a GPT-labelled disk.  However, FreeBSD has its own BIOS-based
> >> bootstrap that can handle GPT-labelled disks.  I doubt the SuperMicro tech is
> >> familiar with that case.  I thought I heard that some folks had added GPT
> >> support to grub as well.
> > 
> > However, this won't boot disks larger than 2TiB, right?  At least not
> > without BIOS support...
> You won't be able to boot from a partition more than 2TiB in, but you
> should still be able to boot as long as you boot from the front part of
> the disk.

John or Marcel can correct me, but I don't think that this is an issue.
The bootstrap is located in the pmbr in sector 0 and the GPT headers and
tables are in sectors 1 - 34.  The bootstrap code knows how to read the
GPT tables and can deal with > 2 tb lba's.

So, as long as you can successfully load the bootstrap code from sector
0, all *should* be good.


> -- Brook
Robert Noland <rnoland at>

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