Re: [ANNOUNCE] GNU fileutils 4.1

[Dave Dittrich]

Paul and Jim,

Sorry this has taken so long.  I've been swamped lately, and just took
a week working vaction in Seoul, South Korea, last week.  Both you and
Jim asked for feedback and the patches.

> Perhaps you might resend it to bug-fileutils.

I am working with some others (copied on this message) on cleaning up
and finishing the patches a little more.  I'll send them to you as
soon as we are done.

> I'd like to see an
> explanation of why this feature is needed in dd.  You can already do
> something like the following to calculate checksums of part of your disks:
>
>   dd ibs=1024 if=/dev/hda1 count=1 | md5sum

Consider doing that for a 30GB drive before you copy each partition,
then again after you copy them to disc/tape, and/or piping them over
the network at the same time.  It can mean the difference between
spending 2 hours imaging a system vs. 6 - 8 or more hours.  The
greater the size of disc and slower the copy medium (e.g., 4mm DDS-1
tape), the more time and trouble it is.

Also I added the feature of generating an MD5 checksum for each block
read at the same time as checksumming the entire stream.  In court
cases, if you have a bad block on the original disc or in your copy
(which means the MD5 hash of the entire contents is now changed) and
have no way of proving that *only* the one block is bad (by showing
that checksums of all other blocks still match), you may end up losing
that entire drive as evidence.  I want to have a method of maintaining
chain of custody and integrity throughout the process of imaging and
file transfer, even in the face of bad media or one lost/damaged
CD-ROM out of a set of N.

The admissibility of a tool in court is partly a function of its
widespread acceptance and use in the industry, which is another reason
to have it in dd, rather than in scripts wrapped around dd/md5sum.

--
Dave Dittrich                           Computing & Communications
address@hidden             Client Services
http://staff.washington.edu/dittrich    University of Washington

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