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Date:      Mon, 26 Aug 1996 17:17:42 +0200
From:      "Julian H. Stacey" <jhs@freebsd.org>
To:        Bora Akyol <akyol@wireless.Stanford.EDU>
Cc:        joerg_wunsch@uriah.heep.sax.de, freebsd-current@freebsd.org (FreeBSD-current users), hoek@freenet.hamilton.on.ca
Subject:   Re: Help on block size in tar 
Message-ID:  <199608261517.RAA16960@vector.jhs.no_domain>
In-Reply-To: Your message of "Sat, 24 Aug 1996 10:06:40 EDT." <199608241406.KAA03455@james.freenet.hamilton.on.ca> 

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Hi, Reference:
> From: hoek@freenet.hamilton.on.ca 
> Subject: Re: Help on block size in tar 
> Date: Sat, 24 Aug 1996 10:06:40 -0400 (EDT) 
> Message-id: <199608241406.KAA03455@james.freenet.hamilton.on.ca> 
>
> In Email, J Wunsch <j@uriah.heep.sax.de> wrote:
> > > > What is the default blocksize of tar on FreeBSD, I have made a tape
> > > > on a freebsd system and now cannot read it on a linux system.
> > 
> > > it may be more complicated...
> > > it might be teh TAPE DRIVE complaining...
> > 
> > Anyway, i think the default blocksize is only 512 bytes.  This should
> > also pass any variable-length driver.
> 
> Are you sure?  I quote the tar manpage (which, being GNU tar isn't the 
> official source of information regarding tar, I suppose).

tar --help
says:
	-b, --block-size N      block size of Nx512 bytes (default N=20)
so it is official.

> "and 20 is the default block size"
> 
> And each of these blocks are then 512 bytes, I believe.
> 
> Or the manpage is just confusing the heck out of me.

Maybe the tape drive used for writing was capable of variable blocking
(like my 
	"TANDBERG  TDC 3800 =04Y" type 1 removable SCSI 2
	Sequential-Access density code 0x0,  drive empty 
)  If one writes a tape on that without `mt blocksize 512', and then tries to
read it elsewhere, problems can occur.... so maybe the tape was written
with variable blocking.

Julian
--
Julian H. Stacey	jhs@freebsd.org  	http://www.freebsd.org/~jhs/



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