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Path: utzoo!linus!decvax!ucbvax!ucdavis!lll-crg!seismo!harvard!talcott!wjh12!pixel!vsh
From: vsh@pixel.UUCP (vsh)
Newsgroups: net.wanted
Subject: Re: more robust tar (or how to live with bad tapes)
Message-ID: <21@pixel.UUCP>
Date: Thu, 17-Oct-85 10:48:03 EDT
Article-I.D.: pixel.21
Posted: Thu Oct 17 10:48:03 1985
Date-Received: Sun, 20-Oct-85 08:49:08 EDT
References: <759@bgsuvax.UUCP>
Organization: Pixel Systems Inc., Woburn, Mass.
Lines: 33

> Has anyone modified 'tar' to handle and recover from tape errors?
> The 'Oh, I found an error and I quit' story is getting real old.  If
> I don't hear from anyone else, I will see what I can do and post the
> diff's to the net.

I don't know if this will work for you, but ...

On Pixel systems we use cartridge tapes, which behave as mag-tape
look-alikes (or so it is claimed - I have never worked on a "big"
machine with a real nine-track tape, so I have no basis for verifying
this claim).  Since /dev/rmt4 and /dev/rmt12 operate in non-rewind 
mode, we do:

	tar -xvf /dev/rmt4

wait for the tape read failure, then repeatedly do:

	tar -xvIf /dev/rmt4

Sooner or later (usually) the tape advances beyond the bad section 
and extraction of files resumes.  We also use this technique to
get to the end of a (new) archive and then extract from the tail end 
of an older archive:

	tar -tf /dev/rmt4 > /dev/null
	tar -xvIf /dev/rmt4

Good luck.
-- 
Steve Harris  
Pixel Systems Inc.; 300 Wildwood St.; Woburn, MA.  01801
(617) 933-7735 x2314 (work)   (617) 664-0099 (home)
{allegra|ihnp4|cbosgd|ima|genrad|amd|harvard}!wjh12!pixel!vsh