"secure-delete" consists of four tools : srm (the secure version of rm), sdmem (wiping memory), sfill (wiping free space in HDD), sswap (wiping swap partition)

$ apt-get install secure-delete

$ srm <path to the file>

==> by default, srm overwrites the content 38 times. you can add a final iteration of zeros as before, with the -z option

==> and recursively with -r option

$ sdmem

$ cat /proc/swaps

$ swapoff </dev/XXX>

$ sswap </dev/XXX>

$ swapon </dev/XXX>