*BSD News Article 7716


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From: dejesus@archimedes.nwc.navy.mil (Francisco X DeJesus)
Subject: HELP! problem with tar PC <-> SUN
Message-ID: <BxJ7qx.2An@avalon.nwc.navy.mil>
Sender: usenet@avalon.nwc.navy.mil (NWC News Admin)
Organization: Science Applications International Corp.
Date: Wed, 11 Nov 1992 03:16:09 GMT
Lines: 41

Hello. I am posting this question regarding a problem a friend of mine is
having in hopes someone out there may be able to help. Here's the situation:

There is a Sun Sparc 2 (SunOS 4.1.2) and a PC running Unix, and we have to
be able to use "tar" to transfer files on a tape (Exabyte 8mm 8200) from
one machine to the other and back. The "PC running Unix" refers to trying
this with SCO Unix, Interactive Unix, and Intel Unix.

Here's the problem: there appears to be a 10x differential in the blocking
factor used by the Sun and the PC's. If a tape is written on the Sun with
a blocking fator of 2, the PC reads it as a blocking factor of 20. Both
"say" they are writing with block size=512 and blocking factor=20 by 
default, but the evidence shows this to be wrong. The Sun at least is smart
enough to recognize the different blocking factor when reading the tape
and has no trouble. The PC, however, has to be told, and this is where the
*REAL* problem comes in:

The client specifies that the "tar" command *HAS* to be used _WITHOUT_
telling it a specific blocking factor on either end (tar xb [blocksize] is
not allowed). I know, I know... it's retarded, but those are the client's
specs. We wouldn't have a problem using the blocking factor command-line
argument, they would. ARGH!

Both SCO and Interactive Unix have an optional file, /etc/defaulttar (sp?),
which is *supposed* to be able to allow default command-line arguments to
tar to be specified there. If this worked, it would have been great... but
no luck. Anyone know how to make this work?

So... any ideas? Please, we are wide open to suggestions. ANY possibilities
will be explored... a different tape driver, another PC Unix version, 
rebuilding tar on the PC (if we can get the sources)... anything goes.

Please respond to me via email (I do not read all these newsgroups regularly).
I'll forward the responses to my friend, and will gladly summarize any 
responses I receive to anyone who's interested. 

Thanks very, very much in advance.

-- 
Francisco X DeJesus  ----- S A I C -----  dejesus@archimedes.chinalake.navy.mil
disclaimer: "Opinions expressed here are mine. Typos and errors are all yours."