Date: Tue, 6 Jan 2004 19:43:44 +1030 From: Malcolm Kay <malcolm.kay@internode.on.net> To: "Sergey 'DoubleF' Zaharchenko" <doublef@tele-kom.ru> Cc: FreeBSD <freebsd-questions@freebsd.org> Subject: Re: "Cannot find file system superblock" error - how to recover? Message-ID: <200401061943.44734.malcolm.kay@internode.on.net> In-Reply-To: <20040106073519.54620420.doublef@tele-kom.ru> References: <20040106002948.38813.qmail@web41102.mail.yahoo.com> <200401061329.26665.malcolm.kay@internode.on.net> <20040106073519.54620420.doublef@tele-kom.ru>
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On Tue, 6 Jan 2004 15:05, Sergey 'DoubleF' Zaharchenko wrote: > On Tue, 6 Jan 2004 13:29:26 +1030 > > Malcolm Kay <malcolm.kay@internode.on.net> probably wrote: > > On Tue, 6 Jan 2004 10:59, Scott I. Remick wrote: > > > Sorry for the delay... holidays had me busy. > > Me too:) > > > > Hopefully you're still around > > > and interested in picking up where we left off. I think we're > > > definitely onto something... > > > > Looking back over some of your e-mails I find: > > QUOTE > > su-2.05b# disklabel -r /dev/ad6s1c > > # /dev/ad6s1c: > > 8 partitions: > > # size offset fstype [fsize bsize bps/cpg] > > c: 156344517 63 unused 0 0 # "raw" part= , > > don't edit > > e: 156344517 63 4.2BSD 2048 16384 89 > > partition c: partition extends past end of unit > > disklabel: partition c doesn't start at 0! > > disklabel: An incorrect partition c may cause problems for standard > > system utilities > > partition e: partition extends past end of unit > > > > That doesn't look good. > > ENDQUOTE > > > > The 63 offset is spurious. I've seen this before somewhere but can't > > remember the details -- i.e the value 63. > > I know where you've seen this. The normal offset for the first *slice* > is 63 sectors, for some historical reasons (those extra sectors were to > be used for bad block replacement or something like that). > Yes, I expect it in the output from fdisk. Ignoring for the moment that the BIOS ideas of geometry has nothing=20 to do with the physical reality; all slices start at sector 1 of a track = so having used sector 1 of the first track (cylinder 0 head 0) for the MBR, the fir= st slice must start at cylinder 0 head 1 sector 1; usually an offset of 63 with th= e assumed virtual geometry. (Nothing to do with bad block replacement which on modern drives is almos= t=20 completely hidden) But I have seen the 63 before in corrupted disklabels, not just slice pos= itions. > Not sure how the 63 made it into the disklabel, though. Neither do I. Malcolm Kay
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