[no subject]

Yes

> > 
> > > 2) Locate the defect sector (dd to /dev/null with offset,counts...)
> > 
> > > 3) Write zeroes to the defect sector to "repair" it and fsck..
> > 
> > I understand the writing zeroes to the bad sector using an offset, but
> > how do I exactly determine how many zeroes to write ?

Mhhh... doesn't dd tell you how many bytes it copied?
Then with a block size of 512 bytes and a block count of one you can use
iseek to try to copy sector by sector.

 
> > Also, I assume you recall that fsck gives no error message now.

fsck only reads meta data - it does not try to read the actual file
data. If you are really,really lucky the bad sector is even unallocated.

> > > 4) Restore the file that was not readable in 1)
> > >
> > > I believe that there are disk repair tools in the ports tree but never
> > > had the need to try them.
> > >
> > > > What's goin' on here and how can I remedy it. This is my gateway server
> > > > and I urgently need to resolve this.
> > > >
> > > > Appreciatively,
> > > >
> > > > Courtney
> > > >
> 
> Basically it sounds like your disk crapped out.
> 
> Trying to salvage the old disk itself is likely a waste of time and
> will lead to future problems.

Yes and no.
A single read error does not mean that a disk is crapping out.
On most IDE disks the specs rate one bit error in 10^14 bits. (SCSI is
usual 10^15)
A power failure while writing a sector will also destroy a sector.
I believe 20% of disks returned to some manufacturers are just send out
again after testing without any repair being done.  


> I know you were trying to make a backup, but do have a recent one you
> could use?
> 
> If you do have to disk recovery of the data, I would reperform your dd as:
> 
> dd if=/dev/orig of=/dev/target conv=noerror,sync
> 
> Then run fsck etc. on the new disk.  Or better yet on a cc copy of the
> new disk.  ie. Save away the dd image for repeated recovery attempts.

I totally agree.

> In the above, noerror says to continue copying even in the presence of
> errors.  sync says to fill the failed read blocks with zeros. 
> (Default behavior is to skip the block.  Very bad if you need to
> reconstruct the filesytem because the offsets will be wrong.)
> 
> You can also try dd_repair (I think).  I have not used it, but it is
> designed to get data off of a failing disk.
> 
> Greg


</pre>
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<ul><li><em>From:</em> ccthomas at joimail.com (Courtney Thomas)</li></ul></li>
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<ul><li><em>From:</em> ccthomas at joimail.com (Courtney Thomas)</li></ul></li>
<li><strong><a name="00374" href="msg00374.html">[ale] dd &amp; unexpected soft update inconsistency, HUH ?</a></strong>
<ul><li><em>From:</em> ups at tree.com (Stephan Uphoff)</li></ul></li>
<li><strong><a name="00377" href="msg00377.html">[ale] dd &amp; unexpected soft update inconsistency, HUH ?</a></strong>
<ul><li><em>From:</em> ccthomas at joimail.com (Courtney Thomas)</li></ul></li>
<li><strong><a name="00378" href="msg00378.html">[ale] dd &amp; unexpected soft update inconsistency, HUH ?</a></strong>
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