Maybe your disk on /dev/sdb has been modified by udisks or another process of your OS (automatically mounted for example).
Maybe the image is the image of a partition and not the whole hard disk.
You can compare yours disks with fdisk:
fidsk -l /dev/sdb
fdisk -l /path/to/image
See the numbers of blocks (and their sizes) maybe it will correspond to a only one partition.
Retry the md5sum on the concerned partition on /dev/sdb:
md5sum /dev/sdbx (x is the number of the partition)
and compare with the md5 of your image
Your source HDD does a size of
660297728 bytes (660 MB) so when you have done the dd, it was:
dd if=/dev/sda of=/path/to/image
So the image has the same size of the entire source hdd:
If you do a md5sum of the source HDD and image it must be the same.
When you copy the image to the new HDD, you do:
dd if=image of=/dev/sdb
But sdb has a size of 1 TB, so:
- the first
660297728 bytes has been written by dd
- the next
440 MB has not been written, the data are the same before dd maybe some zeroes or other.
If you do a md5sum on the entire sdb, you will include the
440 MB which has not been written and the result will not be the same of the md5sum of image.
If you want to do the md5sum of the new disk, you do:
dd if=/dev/sdb bs=512 count=660297728 | md5sum.
The result must be the same.