tar error unrecoverable?

[Karl Auer]

On Sat, 2014-01-25 at 22:05 +0000, Colin Law wrote:
> On 25 January 2014 20:02, Curt Tresenriter <ctres at grics.net> wrote:
> >> > Earlier I tried using dd with the noerror option to copy back to
> >> Why are you using noerror?  If dd shows read errors then there is no
> >> point carrying on.
> > My understanding was that the option would allow me to get whatever
> > files are not corrupted out of the archive.

Whoa, crossed wires here.

dd lets you take a copy of a file while skipping any errors. Yes, you
end up with some damaged areas in the file. But bzip2 compresses in a
block format; even if some blocks in the compressed file are damaged,
you can use bzip2recover to extract data from the blocks that are not
damaged. So it makes sense to use dd to get a reliable, if damaged, copy
of the file, then use bzip2recover to extract what you can from the
damaged copy.

> most likely end up with a file with a bit missing or wrong.  It may be
> possible to recover data from the file, but don't bother unless you
> really need to.

Well, I guess he really needs to, or this conversation would have been a
lot shorter :-) He's got upwards of 40Gb in one compressed file, so
unless the damage is very widespread, or the individual files in the
compressed version are very large, there is a good chance that he can
recover a lot of the original files.
 
Regards, K.

-- 
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Karl Auer (kauer at biplane.com.au)
http://www.biplane.com.au/kauer
http://twitter.com/kauer389

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