[CentOS] Utility to zero unused blocks on disk

[EGO-II.1]

On 02/08/2016 07:38 PM, Always Learning wrote:
> On Mon, 2016-02-08 at 14:22 -0800, John R Pierce wrote:
>
>> the only truly safe way to destroy data on magnetic media is to grind
>> the media up into filings or melt it down in a furnace.
> I unscrew the casing, extract the disk platter(s), slide a very strong
> magnet over both sides of the platter surface then bend the platter in
> half.
>
> How secure is that ?
>
> I can't afford a machine that grinds everything into dust particles.
I have seen a guy in the I.T. department where I  work take a hard 
drive....remove as many stickers from it (to make it porous as possible) 
and then soak it in a "brine" of ammonia, hydrogen peroxide, bleach, and 
salted water...for like a week or two. Afterwards? total useless junk.

EGO II