Questions about dump/restore to/from DVD media

[Ronald F. Guilmette]

In message <20121105021817.fc5bff1b.freebsd at edvax.de>, 
Polytropon <freebsd at 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.

>The command "growisofs -Z /dev/cd0=<file>" will record the file "like
>an image" to the media. In most cases, that would be an ISO-9660 file
>system, like "growisofs -Z /dev/cd0=stuff.iso" (with a premastered
>file stuff.iso). In _this_ case, the input data is read directly from
>file descriptor 0, stdin. Whatever appears there, it will be written
>to the media.

Ah!  OK.  I see now.  Thank you.


>> 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? 
>
>As far as I know, direct device access for writing does not work here.

Yes, apparently not.  Bit I _did_ just find something rather interesting
in this context.  Look at this:

    http://sg.danny.cz/sg/ddpt.html

I have no idea why it isn't already in the ports tree.

I'll probably try it out and see if it works.

>> 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.

>> 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.

(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.)