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Date:      Sun, 04 Nov 2012 16:56:58 -0800
From:      "Ronald F. Guilmette" <rfg@tristatelogic.com>
To:        freebsd-questions@freebsd.org
Subject:   Questions about dump/restore to/from DVD media
Message-ID:  <20880.1352077018@tristatelogic.com>

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I would like to make a backup of one of my systems using dump(8) in order
to be sure that I get everything, including all of the obscure file attribute
bits.

I would like to make this backup to a _minimal_ number of DVD+R disks.

What's the proper procedure for this?

In the dump(8) man page, I see the following example:

  /sbin/dump -0u  -L -C16 -B4589840 -P 'growisofs -Z /dev/cd0=/dev/fd/0' /u

There are several problems with this example, as far as I am concerned.

First I have no particular interest in, or need for _either_ an ISO 9660
_or_ a UDF file system on my backup media.  And in fact, that seems to me
as if it is likely to be an utter waste of (precious) space on the backup
media.  Can't I just put the output of the dump command _directly_ onto
the output DVD+R media?  If so, how would I do this?  Would a command
such as the following work?

   /sbin/dump -0u  -L -C16 -B4589840 -P 'dd of=/dev/acd0 bs=2048' /u

If not, why not?  (I  already know for sure that I can _read_ everything
off of a DVD+R using just dd, so it seems logical that I should likewise
be able to write an entire CD using just dd, but I suspect that there may
be more to it that this, since I've never seen any references or examples
anywhere of anybody writing either CDs or DVDs using dd.)

Actually, I just noticed in the dump manpage the -f option.  So would this
work in place of the above command line?

   /sbin/dump -0u  -L -C16 -B4589840 -f /dev/acd0 /u

And if THAT works, then can dump properly sense the actual end-of-media on
/dev/acd0, so that the -B option can just be ommitted?

Another issue is that I most definitely want to use an absolute minimum
of DVD+Rs to store the dump.  So I am wondering how I might be able to
wedge gzip into this whole process.  Could I do something like this?  If
not, why not?

   /sbin/dump -0u  -L -C16 -B4589840 -P 'gzip | dd of=/dev/acd0 bs=2048' /u

Lastly, I want to make a backup of one entire _system_... not just one of
the several partitions that compose that system.  How exactly can I do
this?  I mean sure, I can back up each partition separately, using dump,
one at a time, but if I do that then the logical implication would seem
to be that on the last DVD+R used to make a backup of each of the partitions,
there could possibly be a lot of unused/wasted space which could have been
used to store the first part of the dump for the next partition in turn.
Is there any way to effectively deal with _this_ issue?


Regards,
rfg



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