Date: Thu, 23 Jan 2014 13:00:53 +0100 From: Arrigo Marchiori <ardovm@yahoo.it> To: Warren Block <wblock@wonkity.com> Cc: Ian Smith <smithi@nimnet.asn.au>, "freebsd-embedded@freebsd.org" <freebsd-embedded@freebsd.org> Subject: Re: Creating code slice before disk image in nanobsd Message-ID: <20140123120053.GC27181@snail.casa> In-Reply-To: <alpine.BSF.2.00.1401151214480.83038@wonkity.com> References: <20120629133759.GA19373@snail.casa> <20140114161533.GB19601@snail.casa> <CAJ-VmonKFEvPRimEmA8vnAbXVCYQ16yOftYhq03VJBYB5knotA@mail.gmail.com> <6027B660-1D2E-4058-B87F-83D8225F0DC3@bsdimp.com> <20140116034220.B43023@sola.nimnet.asn.au> <alpine.BSF.2.00.1401151214480.83038@wonkity.com>
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Hello list,
to answer some of Warren's questions, I will describe what the patch
currently does.
I am not a gpart expert, so you can propose your own considerations and
fixes if you know the subject.
On Wed, Jan 15, 2014 at 12:50:33PM -0700, Warren Block wrote:
> On Thu, 16 Jan 2014, Ian Smith wrote:
>
> > On Wed, 15 Jan 2014 07:53:08 -0700, Warner Losh wrote:
> >
> > > I'll take a look at things... It isn't obvious at first blush this is
> > > the right thing to do, but I need to think about it a bit...
> > >
> > > Warner
> >
> > Perhaps an aside, but I'm pretty sure Warren (cc'd) has said that gpart
> > can do anything that fdisk AND bsdlabel can do?
>
> Yes. Although there is an exception: gpart silently forces alignment to
> CHS values on MBR slices, and fdisk does not. So to get a 4K-aligned
> slice requires fdisk. gpart can align BSD partitions inside a slice to
> 4K, but that is a workaround. (I believe gpart should default to CHS
> but use -a alignment or -b values when given for MBR slices, regardless
> of the MBR spec. This becomes increasingly important as 4K drives and
> SSDs become more common.)
I didn't take alignment into account; I just adapted the calculations
to match the parameters required by gpart.
> > If that's so, and the
> > object here is to deprecate fdisk, why not also replace these lines:
> >
> > +
> > + bsdlabel -w -B -b ${NANO_WORLDDIR}/boot/boot ${MD}
> > + bsdlabel ${MD}
> > +
> >
> > with their gpart equivalents?
> >
> > (and no, I don't know what those should be in this context)
>
> To create the initial MBR, probably already done before the code above:
> gpart create -s mbr ${MD}
This is done by the patch.
[...]
> To create a slice and set it active:
> gpart add -s freebsd ${MD} [1]
[...]
> [1] when creating the slice, -a4k or -b1m can be specified but will be
> silently rounded to CHS values
The -b parameter is also used, therefore your note [1] applies.
> gpart set -a active -i1 ${MD}
This is done by the patch.
> To create the BSDlabel inside the slice and write the bootcode to it:
> gpart create -s bsd ${MD}s1
> gpart bootcode -b ${NANO_WORLDDIR}/boot/boot ${MD}s1
> Then BSD partitions can be added with, for example:
> gpart add -t freebsd-ufs -s2g ${MD}s1 [2]
[...]
> [2] when creating BSD partitions, -a4k can be used and they will be
> created with an offset inside the slice to end up aligned
These were kept as the original:
bsdlabel -w -B -b ${NANO_WORLDDIR}/boot/boot ${MD}s1
> For reference, see
> http://www.wonkity.com/~wblock/docs/html/disksetup.html#_the_old_standard_mbr
Regards,
--
rigo
http://rigo.altervista.org
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