Problems with a munged tar tape

[ggs at ulysses.UUCP]

In article <24358 at rochester.ARPA>, ken at rochester.ARPA (SKY) writes:
> I would have mailed but I can't figure out your address.
> 
> Try using mt to skip one file, then dd. It looks like somebody
> overwrote the first part of it. Some tape controllers have automatic
> density sensing so if you do any reads on it at all it will think a
> 1600 bpi tape was mounted.
> 
> 	Ken

If the 6250 BPI tape really had some crud written at 1600, you will
probably have to write a new tape mark at 6250.  The tape drives I
have seen not only sense density, but refuse to change density from
that of the first record.  Since the density is encoded in a
"density id burst" that preceeds the first record, a file skip won't
help.  Try 

: > /dev/high-density-auto-rewind-name

(assuming [bk]sh syntax).  The next trick will be to convince tar to
read the munged file.  I don't have any good solution to that one.
If all else fails, dump the raw tar file onto a disk then edit out
the tar headers.

-- 
Griff Smith	AT&T (Bell Laboratories), Murray Hill
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