Wipe a drive clean

[Andrew Falanga]

On Mon, Jun 23, 2008 at 2:23 PM, Roland Smith <rsmith at xs4all.nl> wrote:
>
> I'm not sure about flash memory, but for a harddrive, simple writing 0's
> is not a secure way to delete data. It can still be recovered.

Actually, this is for an experiment that I want to start with a
"clean" device for.  I'm not actually trying to obtain some level of
security.

>
>> I'd rather not install a port, if I can avoid it.  I
>
> Have a look at security/wipe.

Before reading this, yes I did.  In fact, I even installed it.
However, the first operation appears to be a renaming of the file in
question.  I was doing:

wipe -z /dev/da2

which was being kicked out with "Operation not permitted."  It seemed
to want to move/rename the file first.  I didn't do enough digging to
get around this before reading this e-mail.

>
>
> I think the trick is to use the right block size. Try bs=512 or
> 2048 in your dd command. Use if=/dev/random instead of if=/dev/zero and
> repeat a couple of times. Note that wiping flash drives way will
> shorten the lifespan of the device.
>

The man page says that a block size of 512 is the default, though I
put it on the command line anyway (talk about being paranoid).  My
problem was the input file.  I was using /dev/null instead of
/dev/zero (which I didn't know about until this e-mail).  Thanks guys.

Andy

-- 
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?