New BSD Installer

Kevin Oberman kob6558 at
Sun Feb 19 06:37:05 UTC 2012

On Fri, Feb 17, 2012 at 1:50 PM, Freddie Cash <fjwcash at> wrote:
> On Fri, Feb 17, 2012 at 1:38 PM, Andriy Gapon <avg at> wrote:
>> And just in case:
>> Unified Extensible Firmware Interface Specification Version 2.3.1, Errata A
>> September 7, 2011 says:
>> [snip]
>>> Two GPT Header structures are stored on the device: the primary and the
>>> backup. The primary GPT Header must be located in LBA 1 (i.e., the second
>>> logical block), and the backup GPT Header must be located in the last LBA
>>> of the device.
>> I can not see any ambiguity or openness to interpretation in this paragraph.
> Unless it's specified somewhere else (which is possible), in this
> paragraph, "device" does not necessarily mean "physical disk".  "Last
> LBA of the device" could be interpreted as "last LBA of the GEOM
> provider".
> The beauty of GEOM is that "device" is whatever logical mapping it provides.
> After all, LBAs are logical addresses (it's right there in the name!),
> not hardwired physical sector addresses.  ;)  If they were hardwired,
> then how would internal sector remapping work?  ;)

Please remember that some disks are dual-boot. FreeBSD may understand
geom has the backup one block from the last LBA on the disk, but no
other OS is likely to do so.

Unless I am missing something, this should be a non-starter. Totally
unacceptable. The backup belongs in the last and only in the last LBA
on the physical disk.
R. Kevin Oberman, Network Engineer
E-mail: kob6558 at

More information about the freebsd-stable mailing list