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Date:      Mon, 16 May 2005 15:52:33 -0400 (EDT)
From:      Jerry McAllister <jerrymc@clunix.cl.msu.edu>
To:        virenp@mail.utexas.edu
Cc:        Kris Kennaway <kris@obsecurity.org>
Subject:   Re: Transferring dump file to tape?
Message-ID:  <200505161952.j4GJqXjB027333@clunix.cl.msu.edu>
In-Reply-To: <36710.146.6.178.5.1116269538.squirrel@mail.cm.utexas.edu>

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> 
> > On Mon, May 16, 2005 at 11:36:18AM -0500, Viren Patel
> > wrote:
> >> Hello. I am using 'dump' to backup client filesystems to
> >> a
> >> disk file on an NFS mounted partition, e.g.
> >>
> >>    dump -0aLu -f /bk/var-20050516 /var
> >>
> >> Now I'd like to take the backup file (var-200500516) and
> >> move it to tape (on the NFS server). However I'd like
> >> the
> >> tape to have the data just as if it had been created
> >> directly by 'dump', e.g.
> >>
> >>    dump -0aLu -f /dev/nsa0 /var
> >>
> >> Any way to do this? 
> >
> > You can use dd to write a file to a device (e.g. tape).
> >
> > Kris
> >
> 
> I thought so too, but it doesn't work. When I issue
> 
>    dd if=var-20050516 of=/dev/nsa0
> 
> I get the following error:
> 
> dd: /dev/nsa0: Invalid argument
> 1+0 records in
> 0+0 records out
> 0 bytes transferred in 0.000786 secs (0 bytes/sec)
> 
> Since 'dump' works with /dev/nsa0 I am not sure what the
> problem is.

I would expect the dd to work also.   You may need to do something
with blocksize.   

But, we see that error a lot on different machines while attempting
to write a file to a tape.   We have code that opens the drive and
writes directly to it, other places that attempt to use dd and also
some places that try to cat to the drive.   All of them work most of
the time, but fail consistently on some machines that appear to be
otherwise identical.   We have resorted to numerous tricks to write 
to a tape on a system that is failing, usually to no avail.   The error
you report is the one we see with dd.   I generally don't see any 
other console message or anything that shows in a dmesg.

I would very much like to see someone who really knows about writing 
tapes respond to this.   I have begun to be suspicious that there is 
something weird about the the sa driver or something along the line, 
but don't know enough to really dig it out.   I posted some questions
around 3 years ago, but got no response.

By the way, this has occurred in various versions of FreeBSD from
around 3.2 through 4.9.   I haven't experimented with it on 5.xx yet.

////jerry

> 
> Viren



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