On Thu, 16 Feb 2006 18:31:42 +0800
Willard Van Dyne <wvandyne@hotpop.com> wrote:
I'm trying to properly clone a 4.3GB (it's old, I know) hard disk
which unfortunately has a lot of bad sectors.
[...]
dd if=/dev/hdb of=/mnt/hda7/image.dd conv=noerror,sync
My problem is that the md5 hash of the image file is different from
that of the original
[...]
Can anyone please enlighten me as to what I'm doing wrong?
Willard,
As many others have already said, you are not doing anything wrong using
dd. But have you tried using dcfldd?
dcfldd has an option to hash the output stream instead of the input
stream, so it will hash the datastream from the drive after the
conv=noerror,sync command has padded the bad sector reads. Then the hash
of the image file should match the acquisition hash dcfldd can record for
you.
A command might look like:
./dcfldd if=/dev/hdb conv=noerror,sync hashwindow=1M hash=md5
hashconv=after hashlog=/mnt/hda7/image.dd.hash.log split=640M
splitformat=aa of=/mnt/hda7/image.dd of=/mnt/hdd1/image.dd
And the individual parts of the command are
./dcfldd - the application
if=/dev/hdb - the input device to read from
conv=noerror,sync - continue through read errors and pad the output to
match the input block size
hashwindow=1M - calculate a hash of every 1M and write the hashes to a log
hash=md5 - use the MD5 algorithm
hashconv=after - hash after the conv=noerror,sync operation has
compensated for bad sector reads
hashlog=/mnt/hda7/image.dd.hash.log - the log file for hashes - will
contain a hash of each 1M of the image as well as the entire image
split=640M - optional - to store chunks on CD ROM
splitformat=aa - if you split the image into chunks, the pieces are named
image.dd.aa, image.dd.ab, image.dd.ac etc
of=/mnt/hda7/image.dd. - first copy of the image file
of=/mnt/hdd1/image.dd. - second copy of the image file - to another device
in case one of your drives dies :-(
We always make two copies to different drives as a safety net since we
rarely keep the original drive as evidence.
James
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