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From: Malcolm Kay <malcolm.kay@internode.on.net>
Organization: At home
To: "DG" <david@fielden.com.au>, <freebsd-questions@freebsd.org>
Date: Tue, 16 Dec 2003 20:12:24 +1030
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Subject: Re: how to append multiple dumps to single tape
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On Tue, 16 Dec 2003 12:46, DG wrote:
> On the subject of multiple dumps, how does one append several dumps to =
the
> same tape?  The dump man page does not seem to indicate an 'append' opt=
ion.
>

When you open a tape for writing (or reading) then writing (or reading) b=
egins=20
at wherever the tape happens to be positioned. So one just has to ensure =
that=20
the tape is not rwound after the first dump is written. This is achieved =
by=20
writing the first dump to device /dev/nsa0 (or some other beginning with =
'n'
which means no re-wind on close).

If the tape has been rewound (perhaps to remove the cartridge for storage=
)
then you can reposition the tape using 'mt fsf' followed by the number of=
=20
dumps already written to the tape.

If a tape has been used a number of times there is no way for the system =
to=20
reliably distinguish the end of the valid information from futher junk th=
at=20
may have been written in previous use -- thus for normal tape drives an
'append' command would be quite flakey.

Malcolm Kay