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RE: Problem using dd to clone a hard disk with bad sectors.

Subject: RE: Problem using dd to clone a hard disk with bad sectors.
Date: Sun, 19 Feb 2006 14:44:56 -0800

From: Willard Van Dyne
Sent: Thursday, February 16, 2006 2:32 AM

[...]

My problem is that the md5 hash of the image file is different from 
that of the original HD (acquired via the command: dd if=/dev/hdb 
conv=noerror,sync | md5sum > /mnt/hda7/orig_disk_md5sum.txt)

Can anyone please enlighten me as to what I'm doing wrong?

Did you compare the block counts copied both when you checksummed
the original drive, and when you imaged it?  Is it possible that
a differing number of error sectors was encountered, between the
dd run that made the image, and the dd run that was used to
calculate the checksum?

One of the advantages of using dcfldd versus regular dd, is that it
can calculate the md5 checksum on the fly, thus requiring that the
source drive be read only once.

Also, just to be on the cautions side, I'd recommend explicitly
specifying bs=512, though it is likely the default.


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