>-----Original Message-----
>From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On
Behalf
>Of Hakan Koseoglu
>Sent: Thursday, March 04, 2010 2:54 PM
>To: CentOS mailing list
>Subject: Re: [CentOS] help fdisk and dd
>
>> What is the best practice to remove all data in the disk?
>If you want to securely remove the data, I recommend using a tool like
DBAN.
>If you want to just wipe out the partition & boot sector for a clean
>reinstallation, dd'ing the disk with zero for a couple of Mbytes is
>more than enough.

I second that. Dban is the niftiest thing since sliced bread. Very handy
tool, if a bit slow. But I guess that comes with the territory. 8-)

--
/Sorin
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On 4 March 2010 14:01, Sorin Srbu <sorin.srbu@orgfarm.uu.se> wrote:
> I second that. Dban is the niftiest thing since sliced bread. Very handy
> tool, if a bit slow. But I guess that comes with the territory. 8-)

The ATA Secure Erase command is generally faster but more difficult -
see http://ata.wiki.kernel.org/index.php/ATA_Secure_Erase

Ben
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>-----Original Message-----
>From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On
Behalf
>Of Benjamin Donnachie
>Sent: Thursday, March 04, 2010 3:11 PM
>To: CentOS mailing list
>Subject: Re: [CentOS] help fdisk and dd
>
>On 4 March 2010 14:01, Sorin Srbu <sorin.srbu@orgfarm.uu.se> wrote:
>> I second that. Dban is the niftiest thing since sliced bread. Very handy
>> tool, if a bit slow. But I guess that comes with the territory. 8-)
>
>The ATA Secure Erase command is generally faster but more difficult -
>see http://ata.wiki.kernel.org/index.php/ATA_Secure_Erase

The advantage with Dban is IMO it's simplicity, just boot it from CD, choose
wiping method and let it rip. After a few hours it's done.

In the ATA Secure Erase case, is two minutes the time it takes to erase a
harddrive? I'm not that knowledgable erasing stuff this way.

--
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From: chloe K <chloekcy2000@yahoo.ca>
> What is the best practice to remove all data in the disk?
> ls fdisk ok or use dd

Maybe something like (replace the ?):
- fast but not secure:
dd if=/dev/zero of=/dev/?d? bs=4096
- slow but more secure:
dd if=/dev/zero of=/dev/?d? bs=4096
- n times slower but n times more secure:
for ((i=1; i<=n; i++)); do dd if=/dev/zero of=/dev/?d? bs=4096; done

JD



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> Hi all
>
> What is the best practice to remove all data in the disk?
>
> ls fdisk ok or use dd
>
> Can data be recovered?
>
> and what is the dd command?
>
> Thank you
>

<http://www.dban.org/>

Default with boot and nuke is three (or is it four?) passes, but you can
tell it full US DoD seven passes, which meets all US gov't requirements
for data destruction, and no, you can't get it back.

Alternatively, the answer on another techie mailing list I'm on is that
you could disassemble the disks and use thermite.

mark

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From: John Doe <jdmls@yahoo.com>
> From: chloe K
> > What is the best practice to remove all data in the disk?
> > ls fdisk ok or use dd
> Maybe something like (replace the ?):
> - fast but not secure:
> dd if=/dev/zero of=/dev/?d? bs=4096
> - slow but more secure:
> dd if=/dev/zero of=/dev/?d? bs=4096
> - n times slower but n times more secure:
> for ((i=1; i<=n; i++)); do dd if=/dev/zero of=/dev/?d? bs=4096; done

Oops, for the slow procedures, it is /dev/random instead of /dev/zero...

JD



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Sorin Srbu wrote:
> I second that. Dban is the niftiest thing since sliced bread. Very handy
> tool, if a bit slow. But I guess that comes with the territory. 8-)
>

DBAN runs at wire speed. Its just that disks with 100s or 1000s of
gigabytes take a long long time to fully write.

DBAN's default erase sequence is excessive for modern disks. the old
DOD erase sequences were devised for media that used simple NRZ type
encodings, with RLL encoding methods used by modern disks, they don't
make any sense at all. all you really need is to write the disk with
all 1s, then all 0s, and its about as good as it will get, not even
CSI:Miami will find any actual data on it (of course, if the script
writers need to, they'll invent data out of thin air).


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> Sorin Srbu wrote:
>> I second that. Dban is the niftiest thing since sliced bread. Very handy
>> tool, if a bit slow. But I guess that comes with the territory. 8-)
>>
>
> DBAN runs at wire speed. Its just that disks with 100s or 1000s of
> gigabytes take a long long time to fully write.
>
> DBAN's default erase sequence is excessive for modern disks. the old
> DOD erase sequences were devised for media that used simple NRZ type
> encodings, with RLL encoding methods used by modern disks, they don't
> make any sense at all. all you really need is to write the disk with
> all 1s, then all 0s, and its about as good as it will get, not even
> CSI:Miami will find any actual data on it (of course, if the script
> writers need to, they'll invent data out of thin air).

That may be the case, but the laws and regulations still want that level
of security, due to the regular "one of our people lost a laptop/it was
stolen, and 7 zillion PII* got stolen!!!"

mark "yes, I am working for the gov't"

* PII - personal identity information

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John Doe wrote:
> From: chloe K <chloekcy2000@yahoo.ca>
>> What is the best practice to remove all data in the disk?
>> ls fdisk ok or use dd
>
> Maybe something like (replace the ?):
> - fast but not secure:
> dd if=/dev/zero of=/dev/?d? bs=4096
> - slow but more secure:
> dd if=/dev/zero of=/dev/?d? bs=4096

What is the difference between the above two commands?
Did I miss something?

> - n times slower but n times more secure:
> for ((i=1; i<=n; i++)); do dd if=/dev/zero of=/dev/?d? bs=4096; done

I don't know what "n times more secure" means. Could you
please explain? Does that mean that, with n times as much
work, one can still recover the information?

Mike
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m.roth@5-cent.us wrote:

[...]

> Alternatively, the answer on another techie mailing list I'm on is that
> you could disassemble the disks and use thermite.

Just a hammer, no need to disassemble the case.

Mike
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Oppose globalization and One World Governments like the UN.
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I speak only for myself, and I am unanimous in that!
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