Drive Imaging with dd

[Kareem Shehata]

On Fri, 2003-08-29 at 16:41, Robert Brockway wrote:
> Hmm...good point.  I was trying to get the dd stream non-interrupted
> before sending it to gzip.  How about this:
> 
> gzip -1 `dd if=/dev/hda1 of=shuttlepod.hda1`


I thing gzip has to interrupt the stream, unfortunately.  Oh well,
10Mb/s is about 4x faster than the previous usb solution, and it gets
better compression too.

> > I'm trying to take a complete snapshot of the partition so that if
> > *anything* happens, all I have to do is create the partition, dump the
> > data, and boot.  I'm not certain tar would capture everything, and NT/XP
> > are notorious for doing interesting things with the filesystem.
> 
> I take your point about NT/XP.  I hadn't heard of any weirdness that
> Linux's emulation of these filesystem types didn't cope with.  Might be
> worth checking into further though.
> 
> I'm currently experimenting with tar for this purpose for the backup CD I
> mentioned and I've seen no problems so far.  My test system is Win98 using
> vfat.

With Win9x, this is definitely doable.  Actually, I used to just xcopy
stuff across, once upon a time.  NTFS is a whole other ball of wax. 
Windows does all kinds of funny stuff with the filesystem, but there's
good news.  There's a new version of the kernel driver for ntfs that
supports everything up to XP.  I just did a quick google for mkntfs, and
it looks as though it may be possible.
 
> As I'm sure you're aware the problem with dd is that what you get is an
> image of the filesystem, which means when you dump the image onto a new HD
> you get the old filesystem back, meaning that you may not be able to
> effectively use the full size of the new drive without resizing, or
> something like that.
>
> I'm been working on the assumption that my CD will have all the tools to
> make a fat/vfat filesystem when needed, and then drop the tar file
> back.  The CD itself will carry doco on the procedure, etc.  I can't
> recall offhand if I'd located a unix based tool to make an NTFS.  I
> actually suspect not.

Is this a tool for migration or backup?  I find when migrating boxes,
it's best to reinstall Windows, then pour across any data.  For backups,
I like the idea of a drive image because I'm guaranteed to have
everything on the drive, and restoring is simple.  But that's just my
personal preference.  For less demanding users, simply throwing the tar
file might do the trick.

> I'll look at including dd as alternative backup mechanism.  I suspect it
> would have speed advantages over tar.

dd is an essential tool, even if all you use it for is making floppy's
or cd images.  I wouldn't write scripts around it, as anyone who really
needs it will know how to use it, or use Ghost4Unix.

Let me know how the CD goes.

Kareem

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