Created Nov 15 2005 - Updated
Nov 21 2005
The Hard Disk Shred/Wipe Page
What is this page all about?
A hard disk contains lots of data.
When you pass it on, you should consider shredding or wiping the hard
disk to ensure the data is not easily retrievable.
Why is it important to
shred or wipe a
Shredding or wiping is currently the only method of
securely obliterating the data on your disk
Shredding/wiping overwrites the hard disk making recovering your old
data very difficult if not impossible
I'd like to learn more about the importance of this
An excellent News forge article is here
A great ORIELLY article is here
Security Expert Peter Gutmann has written two excellent articles:
Deletion of Data from Magnetic and Solid-State Memory
in Semiconductor Devices
How can I shred or
wipe my disks?
There are plenty of free and not free software tools for doing this
I'll concentrate on 2 free ones, Shred and DBAN
Shred is part of the GNU Core Utilities
I run shred under Knoppix 3.9
# shred -n 2 -z -v /dev/hdxy
-n 2 Overwrite the partition 2 times with random data
-z Finish with one pass
writing of zeroes
-v Show it's progress
Change x to reflect the IDE drive number (ie /dev/hda)
Change y if needed for a particular partition (ie /dev/hda1)
Be careful !!
# shred -n 2 -z -v /dev/hda will shred all of the first IDE hard
# shred -n 2 -z -v /dev/hda1 will shred only the first primary
partition of the first IDE hard disk
I also used hdparm
to greatly improve the hard disk throughput
I use: hdparm -X66 -d1 -u1 -m16 -c3 /dev/hda
DBAN is Darik's Boot and Nuke
DBAN is a Linux based bootable floppy/CDROM that provides an excellent
Here's a chart outlining DBAN's erase methods, security levels, number
of passes and details
disk filled with zero's
drive-wiping passes with a random byte in the overwrite sequence
changed each time.
three (1, 2 and 7) of the seven passes recommended under the DoD
seven-pass wipe using random characters, complements of characters, and
random data streams.
random-order passes using specific data combined with eight passes
using random data.
Due to changes in the different data encoding schemes now used by
modern hard drives, Gutmann no longer recommends 35 passes. A few
random passes should suffice.
the drive with a stream from a Pseudo Random Number Generator (PRNG)
How long does it take
to erase a disk using DBAN/Shred?
Here's my test bed
Asus A7V8X-X AMB Athlon XP 2000+ (1.6 GHz)
512 MB DDR-SDRAM PC3200
20GB Samsung SV2001H Ultra ATA/100 5400 RPM hard disk
8 Passes 02:19
8 -v /dev/hda
Knoppix 3.9 with hdparm -X66 -d1 -u1 -m16 -c3 /dev/hda
What about a hardware solution?
I used Goggle and found the WipeMASSter from
If you find an error or wish to comment please let me know