Re: [NTLK] dd revisited

From: Jeff Sheldon (jeff_at_jurai.net)
Date: Thu May 13 2004 - 21:24:43 PDT


On Thu, May 13, 2004 at 02:42:15PM -0500, George Bingham wrote:
> made sure it was blank before you copied it back... Did you do this as
> a way of erasing the card completely to test whether you were really
> about to restore to a blank card? Or do you have to do this in order
> to write to the card using dd (in order to restore)?

Just a test/precaution. "dd" does a total overwrite of its matched-size
destination, so you don't need to do anything special first. If you're
writing to a previously-used Newton card, I would at least recommend using
dd to blank a good chunk of space (if not the remainder of the card)
following your restored image, just in case. You should be safe
regardless, but I never trust computers.

> If I were to use your method to copy the contents of my Newton's
> CF card to another CF card, would I have to format the 2nd CF card or
> could I just use dd to write the data to it raw, right out of the
> package, with no formatting?

Results may vary depending on the card maker, but stick to the same size
since you may be guaranteed at least the amount of storage space printed
on the label. You wouldn't want to write a half-full 16Mb image to a 8Mb
card or waste a 32Mb card by using only half of it. Likewise, there's no
guarantee that a full image recorded from one vendor's 16Mb card will
match another vendor's "just below 16Mb of storage but we're marketing it
as 16Mb anyway" card.

For reasons of data integrity, keep in mind that this is a very
brute-force and ugly way of data backup & recovery and I wouldn't
recommend it for much more than use on an individual card. It's also a
FULL read & re-write and many cheaper CF cards don't tolerate this kind of
thing well over an extended period.

It is, however, a start. I'm looking into the feasability of creating a
set of *nix disk utilities much like "mtools". Unfortunately I don't have
a dedicated PCMCIA reader or Linux-based laptop to fool with the linear
cards...yet.

-Jeff

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