[CentOS] Utility to zero unused blocks on disk

Wes James wrote:
> Is there a utility to zero unused blocks on a disk?
>
> CentOS 6.7/Ext4
>
> I saw zerofree, but I’m not sure it would work on Ext4 or even work on
> this version of CentOS.
>
I don't understand the point of doing this. If you want to sanitize the
disk, use dban <dban.org>, which surely approaches industry standard for
the open source answer.

Just zeroing random blocks? Why? If you want to wipe a specific file,
there's shred.

       mark