Disk imaging program?

[John Hupp]

On 6/25/2014 4:41 AM, Nils Kassube wrote:
> John Hupp wrote:
>> On 6/24/2014 4:05 PM, Niles Rogoff wrote:
>>> _x_ imaging of Windows and Linux partitions in a single
>>> image-the-disk operation that includes the boot sector and related
>>> structures _x*_ bootable disc can do offline image backup and
>>> restore
>>> _x**_ image to spanned DVD's
>>> _x***_ good compression
>>> _x_ free for business as well as personal use
>>>
>>> dd
>>>
>>> * ubuntu, slitaz or any other livecd
>>> ** step 1: http://www.computerhope.com/unix/usplit.htm Step 2:
>>> /dev/cdrom *** tar -czf
>> Interesting idea.  Though dd does a slow and heavy sector-by-sector
>> copy, if speed is not an issue, then you address the compression angle
>> with tar.  But I wonder if dd copies currently unallocated sectors
>> with old data in them, and if tar is then constrained to preserve
>> that data in its compression?  If so, then you're compressing data
>> you don't even want.  (I suppose I could begin the whole thing by
>> wiping the free space, but I wouldn't add that step unless it turned
>> out that I need to.)
> You asked for an application that preserves the boot sector, so you
> obviously want something that does sector by sector copy. Therefore dd
> seems to be a sensible choice to me. If you want to keep data only, I
> would suggest to use tar, but then the boot sector is gone.
>
> Furthermore there seems to be a little confusion of what tar does. It is
> not a compression tool but an archive program which doesn't do
> compression on its own. The suggested command "tar -czf" would invoke
> gzip for compression but it wouldn't be useful together with dd IMHO
> because using gzip alone would suffice.
>
>> And can you kindly confirm that dd knows how to prompt for the next
>> split?
> No, I don't think dd can prompt for a split. But I think tar could do
> that - have a look at the -F and -M options.
>
>
> Nils
>
>

And point well taken: it does seem to me that, as a refinement of the 
initial suggested plan, gzip alone should suffice since we are dealing 
with a single-file output from dd and not a collection of files.