Date: Tue, 27 Mar 2012 21:03:37 +0200 From: rank1seeker@gmail.com To: "John Baldwin" <jhb@freebsd.org>, hackers@freebsd.org Subject: Re: BUG: REL 9.0 - 'boot0cfg' fails with providers of non 512 byte sectorsize Message-ID: <20120327.190337.361.2@DOMY-PC> In-Reply-To: <201203261629.58303.jhb@freebsd.org> References: <20120325.150506.135.2@DOMY-PC> <201203261017.41420.jhb@freebsd.org> <20120326.180253.607.2@DOMY-PC> <201203261629.58303.jhb@freebsd.org>
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----- Original Message ----- From: John Baldwin <jhb@freebsd.org> To: rank1seeker@gmail.com Cc: hackers@freebsd.org Date: Mon, 26 Mar 2012 16:29:58 -0400 Subject: Re: BUG: REL 9.0 - 'boot0cfg' fails with providers of non 512 byte sectorsize > On Monday, March 26, 2012 2:02:53 pm rank1seeker@gmail.com wrote: > > ----- Original Message ----- > > From: John Baldwin <jhb@freebsd.org> > > To: freebsd-hackers@freebsd.org > > Cc: rank1seeker@gmail.com, hackers@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@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. So If in above image with custom sector size (4k for 4k HDD) with slices and bsdlabels and world + kernel If I would 'dd' it to BIOS bassed PC and then power on, it wouldn't boot?! > > > 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. > In above example sector has a size of 4k MBR of 512 bytes is written to it, so there are empyt 3,5k of sector 0. What happens upon power on? Domagoj Smolčićhelp
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