Originally Posted by kbp
You could grab the first sector of each drive to ensure no partition info or bootloader is present, from memory bootloader is the first 446 bytes followed by partition table (could be wrong)
dd if=/dev/sdX of=/tmp/disk1 bs=512 count=1
I have used:
dd if=/dev/sdX bs=1M | od -cb >file
The od utility dumps the output (cb ascii/byte). Since zeroing the disk leaves 0s on disk, od will show these as "*" lines meaning they are all duplicate. When you reach the end of the disk od will put the last line on there as well.
Anything non-zero is an incomplete write.
This works as long as the last thing done to the disk is to write a repeating pattern (not just zeros).
This DOESN'T work when a degausser is used - in that case, there IS no data, and to read the disk at all first requires a low level reformat (which doesn't always work - EMP may have damaged the formatter).
Oh - I use 1 MB for the buffer because it is much faster that way than by reading 512 bytes at a time.