Re: dd to backup fat32 drive?

Henrik Carlqvist wrote:

> hazzmat <hazzmat@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>> Can I dd the C drive Fat32 formatted from the laptop to an outfile (eg,
>> drivec.img) on one of the PC's ext3 formatted harddrives, and then
>> reverse that from the drivec.img outfile to a new 2.5" harddrive with
>> one large fat32 partition on it, and will the new drive boot?
>
> If you only do dd on the partition (called something like /dev/hda1) the
> new drive will not boot unless it also has a Microsoft master boot record
> in the MBR. If you do dd on the entire drive (called something like
> /dev/hda) you will also get the MBR including the partition table that you
> will need.
>
> However, both the partition and the master boot record contain data about
> the geometry of the harddrive. If this geometry differs between the old
> drive and the new drive you might not be able to use the dd method.
>
> A safer way to copy the data would be to use some program like tar.
> However, if you are using tar you might lose some attributes like hidden,
> system and archive for files. To restore your tar archive you will also
> have to create a file system on the new disk with a tool like gnu parted
> or mkdosfs. After that you will also have to use a tool like ms-sys to
> make the system bootable.
>
> regards Henrik


Thanks, I was wondering about how the thing would manage to boot. It
sounds like making the image file from the whole disk is the way to go.
For my first attempt anyway that's what I'm going to try. (got the
outfile image done this night, now I need a new drive) I saw something
online about making a "dd" image of only the MBR-it involved strange
blocksize and count arguments
bs=? (I don't think it was 512) count=1, but the posting didn't say how
one would then go about getting the rest of windows system. I guess it
would done just by making an image of the partition corresponding to
drive C: instead of the whole disk.

If I am going to dd the whole disk (/dev/hdc) shouldn't I make a partition
of the same block count# that fdisk sees on the original laptop drive, on
the new drive (which may not be identically sized overall?) Or would the
right thing to do be to make a single large fat32 partition on the new
disk, since the MBR is going to be copied, and just dd the outfile to
the new disk and hope windows can correct any partition size errors when
it boots up?

Also Is there any way to know ahead of time how likely a certain
replacement disk is to work with the whole disk image approach? The
original drive is a Toshiba 15gig model from about 4 years ago. An
identical model of drive could be in new old stock inventories probably
--it would cost as much as a brand new but considerably larger drive I
expect. The owner is impatient to get back to work on her laptop and
knowing as little as I do about this it's difficult to explain to her what
I'm doing and how likely it is to work.

If we just grabbed a new 2.5" drive off the shelf whereever laptop drives
can be found, how likely would it be to fail this disk duplication method?
Very very likely to fail, more likely to fail than not, even odds, more
likely to succeed than not, or quite likely to succeed with a slim chance
of failure?

It's the underlying issue of "geometry" that I can't make sense of to
myself as a quantifiable risk. If the identical model can't be found
new anymore, how can I get a good geometry in the replacement disk?

Would it help to buy the same manufacturer's model of the same time period
but a different size? Like a 30GB model (twice original size) by Toshiba
of similar vintage. Or would sticking close the size 15-25 GB be
smarter without regard to the manufacturer?

Is "geometry" something that would be more likely to be a problem going
from drives from the ATA33 to ATA100 eras, regardless of size or
manufacturer?

I appreciate anything more you guys can tell me--even educated guesses are
more than I've got to go on from my own experience.
--
Get the us government out of my email to reply
.

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