Wipe the free space on media

Linux tools
By default, shred will overwrite the whole drive 25 times!
If you have a 100GB disk, that means writing 2500GB of data.
To just do it once, you would type (hda or sda!)
#shred -n 1 /dev/hda1
but bear in mind that this is less secure.
--------------------------------
# cat /dev/urandom > /dev/hda1
Break w/ Ctrl+c
--------------------------------
# dd if=/dev/urandom of=/dev/hda1
if u want zeros:
# dd if=/dev/zero of=/dev/hda1
---------------------------------
You can "delete" the journal with:
tune2fs -O ^has_journal /dev/hdXX
But can you shred the journal?
=======================
Windows XP Professional
The cipher command can be used to wipe the free space on a drive.
Use the /w: switch.
This command would wipe the free space on drive C:
cipher /w:c
==========================
http://www.dban.org/