fsck unable to read disk sectors

Bernd Walter ticso at cicely7.cicely.de
Mon May 17 14:02:14 UTC 2010

On Mon, May 17, 2010 at 10:54:17PM +0930, Matt Thyer wrote:
> On 12 May 2010 11:16, Bernd Walter <ticso at cicely7.cicely.de> wrote:
> >
> > On Tue, May 11, 2010 at 10:15:13PM +0200, Alexander Best wrote:
> > > i've posted a log here which is pretty self explanatory:
> > >
> > > http://pastebin.com/tn3NiDDW
> > >
> [snip]
> >
> > One of the typical problems users have is that they forget that
> > adding a label takes one sector, so the labeled device is smaller.
> > This is no problem if you create the filesystem on the labeled
> > drive, but often enough people add the label after creating the
> > filesystem.
> FreeBSD's utilities should be able to detect this situation and either
> correct the filesystem size or refuse to apply the label.

How can this work?
glabel doesn't know anything about volume contents - it just writes a
label-sector and offers the remaning storage as a new volume.
Result: Refusing is impossible.
Changing UFS filesystem size isn't an easy task and the last sector is
already lost when filesystem comes into game.
Result: Too late.
I think the only reasonable thing to be done is that fsck can speak
up by checking the volume size with the filesystems size _after_ glabel
has overwritten the last sector.

B.Walter <bernd at bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.

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