[ale] Need an iso to wipe hard drives.

Ed Cashin ecashin at noserose.net
Tue Apr 20 11:42:58 EDT 2010


On Sat, Apr 17, 2010 at 10:20 PM, Doug McNash <dmcnash at charter.net> 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. I wouldn't trust the syncs as much as I would the unmount (gauxrunteed) but that is just me. (I would also flush the hardware disk cache.) Laptops are worse in this behavior as they are configured to write to the magnetic media as little as possible.
>
> If your going to be paranoid, at least be obsessive-compulsive about it.

I'm reminded of an XFS bugfix where sync was added on unmount.

Apparently there have been kernels where the fs was responsible for
doing the sync on unmount but did not.  It made me start recommending
"sync" *after* running umount, because I knew not everybody I was
talking to had that fix, and I didn't know how many other filesystems had
a similar problem.  (I believe that in other kernel versions the fs was not
responsible for the sync because it was handled in the VFS layer.)

So obsessive would be, maybe---sync, unmount, sync.  ;)

-- 
  Ed Cashin <ecashin at noserose.net>
  http://noserose.net/e/
  http://www.coraid.com/



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