[CentOS] Utility to zero unused blocks on disk

Mon Feb 8 22:35:48 UTC 2016
John R Pierce <pierce at hogranch.com>

On 2/8/2016 2:18 PM, m.roth at 5-cent.us wrote:
> dban doesn't? What F/OSS does "secure erase"? And does it do what dban's
> DoD 5220.22-M does?

do you even know what NISP Operating Manual 5220.22-M is?   One thing it 
does NOT have is ANY specifications of methods of data erasure (it 
mentions data erasure in 2 short paragraphs, out of a 140 page book on 

The Defense Security Service C&S-M (clearing and sanitization matrix) 
procedures state that magnetic disks will be degaussed or physically 

note that degaussing a hard drive made since the early 80s will erase 
its servo tracks and render it scrap.

there is no such thing as secure erasure.   the whole silly 3 passes of 
random data followed by zeroing thing has been debunked numerous 
times.   It MIGHT have worked in the days of MFM disks, when block 
sparing was an OS function, and the drives just provided a stream of 1s 
and 0s without recognizing 'sectors' (sectoring was done in the MFM disk 
controller board).    With any modern storage device writing a single 
pass of zeros will do virtually the same thing, and is adequate to 
remove casual data but by no means good enough for any sort of 
government mandated security.

john r pierce, recycling bits in santa cruz