Scrub free disk blocks

[Robert Nichols]

On 08/27/2010 11:53 PM, JD wrote:
>    On 08/27/2010 09:25 PM, JD wrote:
>>   Is there a Linux util to scrub free disk blocks and keep everything
>> else intact ??
>>
> Someone (not on this list) described a simple way to do this.
> Scrubbing files to be deleted is easy enough - there are utils for it
> already.
> But scrubbing existing free space is slower and requires patience.
>
> cd to the root of the partition.
> sudo dd if=/dev/zero of=ZERO bs=20M
>
> When the dd program fails to write any further, you
> have grabbed and zeroed all available free disk blocks
> in the partition.
>
> Now all you do is use the command scrub to scrub the file ZERO
> and when done  the file is deleted.

You need to do that as the UID permitted to use the reserved blocks
if you really want to clear _all_ the free space.  Note that if the
drive has reallocated any bad sectors there could still be some old
data present on the disk.

-- 
Bob Nichols     "NOSPAM" is really part of my email address.
                 Do NOT delete it.