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Date:      Mon, 5 Nov 2012 03:52:33 +0100
From:      Polytropon <freebsd@edvax.de>
To:        "Ronald F. Guilmette" <rfg@tristatelogic.com>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: Questions about dump/restore to/from DVD media
Message-ID:  <20121105035233.e3c4ae8a.freebsd@edvax.de>
In-Reply-To: <21628.1352083063@tristatelogic.com>
References:  <20121105021817.fc5bff1b.freebsd@edvax.de> <21628.1352083063@tristatelogic.com>

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On Sun, 04 Nov 2012 18:37:43 -0800, Ronald F. Guilmette wrote:
> 
> In message <20121105021817.fc5bff1b.freebsd@edvax.de>, 
> Polytropon <freebsd@edvax.de> wrote:
> 
> >> I would like to make this backup to a _minimal_ number of DVD+R disks.
> >
> >If you think you can add compression to your files (if it makes
> >sense), it should be incorporated to the command.
> 
> Yes.  There really ought to be a -z option integrated into both dump and
> restore commands.

Depending on _what_ kind of compression (gzip, bzip2, 7zip, xz etc.)
there might be many of them. If utilizing the capabilities of
libarchive is possible, it would be a nice option.



> >> Another issue is that I most definitely want to use an absolute minimum...
> >
> >Taking the initial approach of
> >
> >/sbin/dump -0u  -L -C16 -B4589840 -P 'growisofs -Z /dev/cd0=/dev/fd/0' /u
> >
> >it could be something like this:
> >
> >/sbin/dump -0u  -L -C16 -B4589840 -P 'gzip | growisofs -Z /dev/cd0=-' /u
> 
> Yes.  I see.  That makes sense.
> 
> But as I said (above) to make this really work right, dump & restore really
> need to have -z options, and do the zipping/unzipping internally.  Only
> if this were available could dump properly deal with end-of-media on any
> given output volume, I think.

The problem is that delegating compression to a "sub-task" would
imply that dump cannot precisely adjust its output to match the
media size (as the limit is now defined by how good the compression
works). Instead an additional step would be required to make sure
that a new media for the _compressed_ data stream is requested
when it exceeds a certain limit. Additionally restore would have
to use a comparable method of "chaining" the multiple volumes,
as it requires operator attention and action.



> >> 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? 
> >
> >At least not with dump. The dump utility operates on file systems,
> >this means "it takes partitions as input". Whatever is _one_ partition
> >can be processed "per step".
> 
> Well, this is entirely sub-optimal.

It depends on how you did layout your system. Using dump + restore
means to operate on partitions. Make the system one partition - deal
with one partition. Make many partitions - need to deal with them
individually.



> (I hate to say it, because in general I loath & despise Windows, but even
> Windows has a built-in facility for making a single backup of an _entire_
> system, and in a single step, *and*, I presume in a space-efficient manner.)

That would be a task for dd. :-)


-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...



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