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Date: Tue, 28 May 2013 19:03:42 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: Lev Serebryakov <lev@FreeBSD.org>
Subject: Re: Could gpart align MBR primary partiton at 4K?
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On Wed, 29 May 2013, Lev Serebryakov wrote:

> Hello, Freebsd-geom.
>
> I'm trying to format external Extended Format drive to FAT32 under
> FreeBSD 9.1-STABLE
>
> I've created MBR scheme, but when I try to create primary partition
> I get:
>
>> sudo gpart add -t fat32 -a 4k da0
> da0s1 added, but partition is not aligned on 4096 bytes
>>
>
> Why?
>
> According to "Using Advanced disks for old OSes like WinCP" guides it
> is possible to 4K-align MBR partition, but all these guides are
> windows-centric...

The MBR standard specifies alignment to cylinders.  gpart complies with 
that.  It's like -a always goes to 63.  Other operating systems are not 
as strict, which at this point makes it easier for their users.

As far as I know, the only way to align MBR partitions on FreeBSD is by 
entering manual values to fdisk(8).