Path: utzoo!yunexus!ists!mike
From: mike@ists (Mike Clarkson)
Newsgroups: comp.unix.xenix
Subject: Re: SCO 2.2.1 tar question
Summary: You don't really want to do this....
Message-ID: <196@ists>
Date: 4 May 88 02:51:51 GMT
Article-I.D.: ists.196
Posted: Tue May  3 22:51:51 1988
References: <100@pigs.UUCP> <508@holos0.UUCP>
Organization: Institute for Space and Terrestrial Science
Lines: 47

In article <508@holos0.UUCP>, lbr@holos0.UUCP (Len Reed) writes:
> in article <100@pigs.UUCP>, haugj@pigs.UUCP (John F. Haugh II) says:
> >
> >> In article <8WQW5Ky00Vs8MSNUQN@andrew.cmu.edu> jl42+@andrew.cmu.edu (Jay Mathew Libove) writes:
> >> | Hi. I'm running SCO Xenix SysV/286 v2.2.1 on an IBM PC/AT clone and
> >> | I am having a bit of a problem with "tar".
> >> | I want to tar off a filesystem as:
> >> |
> >> | % tar cf - /pathname | compress | tar cfk /dev/rfd096ds9 720 -

You don't really want to do this (trust me I know :-).  All flaming
about who's capable of reading the F Manual aside, what you are trying
to do is end up with one big compressed file split over n floppies. All
it takes is one bit to flip and your entire archive is dead. Remember,
compress has no error correction.  At least around here, we find
floppies to be notoriously unreliable, and compress is most unforgiving.

> Better compression be might be achieved by copying the entire heriarchy
> (using cpio or tar), compressing the individual files, and then tarring the
> shadow heirarchy.  Even if the compress step were done as part of the
> heariarchy copy, using a script with a loop in it, you need hard disk space
> for the whole compressed heirarchy.  (This also has the advantage that the
> files on the diskette will be listable using "tar t" or "cpio -t".)
> 
> If you need multiple volumes and don't have the hard disk space for a copy,
> [ valuable shell script solution deleted ]

A much better way to go.  Don't forget that either compress or tar can
suffer errors, but you can recover from tar errors.  dd off the disk and
hand patch or extract the tar file.  Nothing will help you recover from
even a single bit flip in compress.  This way means you'll only lose the
single compressed file with the error.

> There must be better ways to get floppies with compressed archives.
> I haven't used it, but perhaps "zoo" is what you want.

I think what's really needed is a better tar, with error *correction*
built in (CRC or the like).  Maybe someone could graft in a compression
option that was specifically designed to be used with error correction.
True it would cost you some space, but it would be worth it.
See the discussion in comp.sources.d.

-- 
Mike Clarkson						mike@ists.UUCP
Institute for Space and Terrestrial Science		mike@ists.yorku.ca
York University, North York, Ontario,
CANADA M3J 1P3						(416) 736-5611