a new hard-drive in a 2y/o laptop
nightrecon at hotmail.com
Sat Jan 1 00:34:11 UTC 2011
Ian Smith wrote:
> In freebsd-questions Digest, Vol 343, Issue 5, Message: 10
> On Tue, 28 Dec 2010 11:02:45 -0500 Chris Brennan <xaero at xaerolimit.net>
> > On Tue, Dec 28, 2010 at 2:23 AM, Michael Powell
> > <nightrecon at hotmail.com>wrote:
> > > Try zeroing out the mbr:
> > >
> > > Boot a LiveFS CD, then at a root prompt do:
> > >
> > > sysctl kern.geom.debugflags=16 and:
> > >
> > > dd if=/dev/zero of=/dev/adx oseek=1 bs=512 count=1
> > >
> > > where x equals your drive number. This will zero out any old MBR.
> Er, no, Mike. The MBR is in sector 0 of the disk; that would zero out
> sector 1 as oseek=1 skips over sector 0. What's in sector 1 depends on
> how/whether the disk is sliced. In a 'dangerously dedicated' (unsliced)
> disk like a memory stick perhaps, this would usually be /boot/boot1 and
> include the bsdlabel. In a sliced disk, sectors 1 to 62 are typically
> unused, the first slice usually starting at sector 63.
> t23% fdisk -s ad0
> /dev/ad0: 232581 cyl 16 hd 63 sec
> Part Start Size Type Flags
> 1: 63 8385867 0x0b 0x00
> 2: 8385930 125821080 0xa5 0x80
> 3: 134207010 33543342 0xa5 0x00
> 4: 167750730 66685815 0xa5 0x00
> If you really want to zero out sector 0, leave out the oseek (or use
> oseek=0) - but you're better off using 'fdisk -Bi' to init a new disk.
Yes - true enough. Was thinking partition table and typed 'mbr'.
> Mmm .. it's not clear from Chris' original message exactly what he did.
In my case, a temporary replacement disk had FreeBSD 6.2 on it. Something
changed wrt to disklabeling on the way to 8-Release and the old 6.2 being
present created a situation where that region on the disk was invisible to
the new labeling and wouldn't write out. A new install of 8-Release
(sysinstall) would error out with the same message as Chris when it came to
the point of writing out to the disk. For me, the above 2 commands fixed my
situation. Even though his error is the same, I think his problem may be
different from mine.
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