BUG: REL 9.0 - 'boot0cfg' fails with providers of non 512 byte sectorsize

[John Baldwin]

On Monday, March 26, 2012 2:02:53 pm rank1seeker at gmail.com wrote:
> ----- Original Message -----
> From: John Baldwin <jhb at freebsd.org>
> To: freebsd-hackers at freebsd.org
> Cc: rank1seeker at gmail.com, hackers at freebsd.org
> Date: Mon, 26 Mar 2012 10:17:41 -0400
> Subject: Re: BUG: REL 9.0 - 'boot0cfg' fails with providers of non 512 byte 
sectorsize
> 
> > On Sunday, March 25, 2012 11:05:06 am rank1seeker at gmail.com wrote:
> > > I've created a vnode image (md0) with sectorsizes of 8192 and 4096
> > > 
> > > After installing MBR's bootcode '/boot/boot0', in provider 'md0' I did:
> > > # boot0cfg -o noupdate -m 0xc md0
> > > boot0cfg: read /dev/md0: Invalid argument
> > > # boot0cfg -v md0
> > > boot0cfg: read /dev/md0: Invalid argument
> > > 
> > > If custom sectorsize isn't specifed(512 bytes), then both above CMDs 
will 
> > work.
> > 
> > MBR bootstraps (such as boot0) assume a 512 byte sector.  They won't boot 
> > correctly on media with a different sector size.  So even if you "fixed" 
> > boot0cfg, you wouldn't have a bootable system.
> > 
> > -- 
> > John Baldwin
> > 
> 
> 
> Is it so?
> This is also true for '/boot/mbr' file?

Yes.

> Well, majority of PC's are still BIOS bassed so MBR scheme is still around 
and there are also now HDD's with 4b sector sizes and SSD's with 4b and 8k 
sector sizes.
> 
> So how does things work in those cases, without GPT?

The BIOS still emulates 512 byte sectors.

-- 
John Baldwin