Other options:
- BleachBit: http://bleachbit.sourceforge.net/
- secure-delete
Syntax: srm [-dflrvz] file1 file2 etc.
Options:
-d ignore the two dot special files "." and "..".
-f fast (and insecure mode): no /dev/urandom, no synchronize mode.
-l lessens the security (use twice for total insecure mode).
-r recursive mode, deletes all subdirectories.
-v is verbose mode.
-z last wipe writes zeros instead of random data.
- using dd to wipe drives
To overrite data with zeros:
$ sudo dd if=/dev/zero of=/dev/sdX
To overwrite data with random data:
$ sudo dd if=/dev/urandom of=/dev/sdX
