secure wipe

#apt-get install secure-delete

It will provide the following tools for secure wiping:

/usr/bin/srm

/usr/bin/sfill

/usr/bin/sswap

/usr/bin/sdmem

srm - secure remove (secure_deletion toolkit)

$srm file_name

$srm -r folder_name

There is already another tool "shred" comes with "coreutils" package in Debian:
coreutils - GNU core utilities

/usr/bin/shred

shred - overwrite a file to hide its contents, and optionally delete it

$shred file_name

sfill  -  secure free disk and inode space wiper (secure_deletion toolkit)

#sfill /mount_point/

sswap - secure swap wiper (secure_deletion toolkit)

Turn off swap first :

 #swapoff /dev/sdaX
or
#swapoff -a  //to turn off all swap

Now run sswap:

#sswap /dev/sdaX 

sdmem - secure memory wiper (secure_deletion toolkit)


There is some limitation of these tools.
Please use manual pages of individual package for details information.