[PLUG] Imaging CF card...

Rodney W. Grimes freebsd at gndrsh.dnsmgr.net
Thu Aug 8 22:34:16 UTC 2019


> On Thu, Aug 8, 2019 at 10:19 AM Rodney W. Grimes <freebsd at gndrsh.dnsmgr.net>
> wrote:
> 
> > > > Ditto what Tomas said. For looking at it locally, dd'ing the partition
> > > > (/dev/sdb1) is fine, but to make a full backup of the CF card so that
> > you
> > > > can reproduce it, you want an image of /dev/sdb as well.
> > >
> > > That assumes the size of the CF card is the same. I would use fdisk to
> > > partition it and then write the image to sdb1.
> >
> > I would not write an image, but would rather fdisk and format
> > the new empty msdos partition, then use mount(s) and tar to
> > copy the contents.
> >
> > Imaging msdos file systems to changed partition parameters is
> > frought with bad issues.
> >
> >
> If the new media is the same size or bigger, dd'ing the image will work
> fine (you just won't use any more space). It has the advantage of being
> able to restore an exact copy. If I was screwing around with ancient media,
> I would definitely save a full device image and never modify it. You can
> always modify a copy.

Actually that holds true for modern OS's, but when you step back
into the world of things like Windows 98 much of this falls apart,
if the device translated geometry changes because it of a physical
different size you may not be able to access the contents of partitions
properly as there are assumptions in code about the location of
certain critical things based on the device geometry.

A 16 head 63 sector translation blows chunks if the new device
shows up as 255 head 63 sector, which happens when your device
gets above a certain size by most bioses.

One must remeber your stepping back into the pre-dawn of LBA-48
support so there are pitfalls to watch out for.

-- 
Rod Grimes                                                 rgrimes at freebsd.org



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