I am running DBAN now, and after 4 hours, it has already completed 3
passes. After 4 hours, Copywipe had only completed 20% of the first
pass. And DBAN has an error counter that says 0. So that seems
strange.
I believe that DBAN will write all zeros for the last pass. After it
is done, is there any way for me to verify that it actually wiped the
drive, and that the drive has all zeros?
If each sector contained nothing but zeros, then you'd have a slightly
easier time to verify the disk. For example, if the data was streamed
into a checksumming tool, then the end result should be a grand total
of zero. If some other programmatically created data pattern is used,
then you'd have to write a tool to verify that the pattern is reproduced.
If I was doing this verification project myself, and I couldn't find
a tool to automatically verify what was written, I might head to
Linux land. Writing programs to work on storage devices isn't that
hard - it really depends on how rusty you are, as to how long it would
take. And the program wouldn't necessarily have to be that long either.
As a friend at work would quip - "yup, that needs a three line program".
To give you a hint, at least in Windows land, there is a port of "dd".
Apparently "dd" can be instructed to copy to "standard out", so if
you piped the output into another Windows tool, like a checksum program,
you might just be able to compute a checksum over the entire data
stream. If the data on the sectors was supposed to be zero, then the
results should be zero.
http://www.chrysocome.net/dd
On my Windows disk, I have a small collection of GNU tools, such as
"coreutils", and in there, I have a copy of "sum.exe". Perhaps "dd"
could be piped into a copy of "sum" from coreutils.
Since "dd" is part of Linux as well, you could also use the same concept
with a Linux LiveCD. (Knoppix and Ubuntu can be booted from their
respective CDs, and you can keep a few small files on a removable
storage device, while working with them. The LiveCDs don't have to
be installed to a hard drive, to do useful work.)
My suspicion is, that DBAN doesn't leave zeros on the disk for all of
its erasing options. At least some of them will have used the
Mersenne Twister, to make random data. (I tried to find a nice manual
for DBAN, but all I found was text files of one sort and another.)
Your first task, might be to find a sector editor and look at just
a couple sectors, to see what kind of a mess you're dealing with.
(I.e. Whether sectors are zeroed, or contain random data.)
"dd" can also be used to write zeros to a drive. In fact, that is
what I've used it for recently, as a means of erasing the "front part"
of a disk drive. Using "/dev/zero" as a source of data, you can
instruct dd to transfer "/dev/zero" to the hard drive, which will
overwrite the drive with zeros. If you then streamed the data to
standard output and piped it to a checksum or to a "word count" program
such as "wc", then you can compute the checksum of all the data,
and also verify the byte count available from the drive. So
there are "toy" programs, and bits and pieces of solutions around.
To use "dd" in Linux to write zeros, this is what you do.
1) Boot Knoppix CD into Linux desktop.
2) Open a terminal window. Type
sudo dd if=/dev/zero of=/dev/sda bs=512 count=10000
That fills the first 10000 sectors with zeros. The command
syntax assumes /dev/sda is the disk to be hammered. Any time
I'm doing this kind of "surgery", only the disk to be hammered
is connected to the computer. Then, I can't possible make
a mistake with my selection of "/dev/sda" and hammer the
wrong drive. (That is one thing that worries me about using
the "dd" port in Windows - my boot drive would be a sitting
duck if I made a mistake typing in the command. Not so with
a Linux LiveCD, as the CD can't be erased.)
After your erasure pass is complete, then you could use dd
again, to read /dev/sda and pipe the output into checksum
or wc, to compute a checksum and to verify the total number
of bytes read, respectively. (A Linux/Unix guru can easily
improve on the above suggestions. I don't use this stuff
enough any more, to be good at it.)
Have fun,
Paul
