Hi DU Admins
Thanks to Judd (reiffin_at_ic.eecs.berkeley.edu), Brian Sheehan,
Bernt Christandl, Jim Belonis, Alan Rollow, Volker Hejny,
Lucio Chiappetti, Tim W. Janes, BigRedDog (ckrieger_at_latrade.com),
Jim Wasden, mlroberts_at_dow.com, Pirie Hart, Ken Weiner, Dr. Tom Blinn
and anyone else whose replies I'm yet to receive.
I now understand what bsf does. It is the mirror image of fsf.
`mt fsf' leaves the tape at the point just past the EOF mark - that
is at the start of the next file. `mt bsf' leaves the tape before
the previous EOF mark - that is at the end of the previous file.
To get from the start of one dump image to the start of the
previous image you need to do `mt bsf 2' followed by `mt fsf 1'
to get on the right side of the EOF mark.
In my case after a `restore -t' the tape is somewhere in the middle
of a dump image so I need to do `mt bsf 1' and then `mt fsf 1' to
get back to the start of the current image. This works (I've
tested it) for every image but the first on a tape. For the first
image you have to use `mt rewind'.
The point of all this was to get listings and check sums from a set
of dump images in one pass through the tape. It looks like this
is not such a great idea. It won't necessarily save time or wear
and tear on the tape. I think I'll stick with the current two pass
strategy.
A couple of suggestions related to the subject of backups in general
rather than to my specific question.
Jim Wasden said:
> Why don't you run POLYCENTER NetWorker Save and Restore? The
> "SingleServer" version of this product comes free with Digital
> UNIX and is a hell of a lot better that "dump and restore".
> Check the "Additional Subsets" section (usually Appendix C) of
> the Digital UNIX Installation Guide...
and mlroberts_at_dow.com said:
> Try looking into BRU from EST. It is much more reliable than dump and
> handles media errors wonderfully. Tell them I sent you and they may send
> you a mug. The software is affordable and runs on all unix flavors. It
> can certainly do what you want in this case and a whole lot more..
Finally a couple of people wanted to know what commands I use to
get a check sum while making a dump. I use a script for this.
Since most of the backups are made to a tape drive on a remote host
the sequence of cammands is like this:
/usr/sbin/mknod /var/tmp/CheckSum p # Create a named pipe
{ sum /var/tmp/CheckSum >&2 & /usr/sbin/dump -f - -0un -b 32 /usr/users |
tee /var/tmp/CheckSum | rsh kelvin "dd bs=32k of=/dev/nrmt0h"; } 2>&1 |
tee -a /tmp/dump.log
If you're dumping from the host with the tape drive (kelvin in our case)
this can be done more simply without the need for a named pipe. You
just need to do:
/usr/sbin/dump -0unf - | tee /dev/nrmt0h | sum ...
Thanks again
Ian
_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
_/ Ian Mortimer _/
_/ Email: mortimer_at_physics.uq.edu.au ,-_|\ Department of Physics _/
_/ Tel : +61 7 3365 3436 / *\ University of Queensland _/
_/ Fax : +61 7 3365 1242 \_,-._/ St. Lucia, Brisbane _/
_/ v Queensland, Australia 4072 _/
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Disclaimer: Any opinions expressed are my own.
Received on Wed May 07 1997 - 04:31:22 NZST