Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!ncar!asuvax!anasaz!duane
From: duane@anasaz.UUCP (Duane Morse)
Newsgroups: comp.unix.wizards
Subject: Re: fsck fails...help!
Summary: Advice probably not appropriate for 4.3BSD, but trick worth knowing
Keywords: fsck
Message-ID: <730@anasaz.UUCP>
Date: 17 Sep 89 15:05:13 GMT
References: <9171@pyr.gatech.EDU> <726@anasaz.UUCP>
Organization: Anasazi Inc., Phoenix AZ
Lines: 34

In article <726@anasaz.UUCP>, duane@anasaz.UUCP (Duane Morse) writes:
) In article <9171@pyr.gatech.EDU), david@pyr.gatech.EDU (David Brown) writes:
) ) 
) ) Help!!  Fsck is failing on my machine.  I get the following error:
) ) 
) ) CANNOT READ: BLK 16 (CONTINUE)
) ) 
) ) In my trusty 4.3BSD System Managers Manual, I find that "...This
) ) should never happen.  See a guru." 
) 
) The message means that it cannot physically read the block. I don't
) know how fsck varies from one system to the next, but the version on our
) NCR Tower 32/600 also stops when this happens.
) 
) The only time this occurred on our system, I made a lucky guess about
) something and 'fixed' the problem. In particular, I determined which
) physical blocks the message referred to, verified the problem by trying
) to dd the block, and then, as root, wrote zeroes to the bad block. My guess
) was that either the smart SMD controller would allocate an alternate
) block when I tried to write to the bad one, or the sector/block
) checksum was bad and writing to the block would put out a good checksum.
) After this I could run fsck.....

I received mail informing me that block 16 for 4.3BSD is in the superblock,
so clearing the block would probably have dire consequences. I've never
been near 4.3BSD; my comment is based on a trick that worked the only
time a similar problem arose on our system, which runs SysV. If block 16
is part of the superblock, it'd be worth a quick check to see if rewriting
the block with "reasonable" data is feasible.
I keep a printout of the superblock on our system for that reason. 
-- 

Duane Morse	...{asuvax or mcdphx}!anasaz!duane
(602) 861-7609