[ale] Need an iso to wipe hard drives.

[JK]

On 4/17/2010 8:20 PM, Doug McNash wrote:
>
> ---- Chris Fowler<cfowler at outpostsentinel.com>  wrote:
>> I also used to have a program that I wrote which would open a file for RW and fill it with
>> random stuff.  If would seek back to the beginning and repeat a few times then close and
>> finally delete.
>
> Unless this file is much bigger than the RAM used for file buffer caching (which on linux is
> quite a large percentage) not much is actually being written to the magnetic media unless you do
> a sync, fsync or unmount the drive.


Except that there's a kernel thread that writes dirty buffers
to disk periodically.  The semantics of the "sync" system call
are, "Write all dirty buffers to disk and don't return until you're
done". But in normal operation I'd be astonished if most dirty
buffers weren't written out within a few seconds, even without an
explicit sync.  Only if something was writing data faster than
it could be sent to disk, would there be much danger of having
a lot of dirty buffers in RAM for any length of time.

Don't know about hardware disk caches, but that's what happens
in the kernel. (Unless things have changed a whole lot since
2.4.)

-- JK

-- 
Forget Jesus: stars died so that you could be here today.
  - physicist Lawrence Krauss