dod 5220.22 is only how I wipe drives.<br><br><div class="gmail_quote">On Wed, Jun 1, 2011 at 12:06 PM, David L. Willson <span dir="ltr"><<a href="mailto:DLWillson@thegeek.nu">DLWillson@thegeek.nu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Chris is right. Unless you have a week to spend on this, you'll do well to restart with /dev/zero and dd.<br>
<br>
Also note that you ~can~ get dd to output progress! If you can send the process a USR1 signal (or a SIGUSR1) and it will output it's current progress. That can be pretty handy for estimating the completion time. How to get the signal there? Here's an example:<br>
<br>
dlwillson@dlwillson-laptop:~$ dd if=/dev/zero of=/dev/null bs=8M &<br>
[1] 6276<br>
dlwillson@dlwillson-laptop:~$ killall -SIGUSR1 dd<br>
dlwillson@dlwillson-laptop:~$ 1785+1 records in<br>
1785+0 records out<br>
14973665280 bytes (15 GB) copied, 6.81347 s, 2.2 GB/s<br>
<br>
Also, you can (or could have) saved a ~bunch~ of time by just clearing the first several meg of each partition (and optionally, the disk). Unless you're very interesting, to an extremely smart, wealthy, or lucky person, over-writing file data is over-kill. Destroying the filesystem and partition meta-data is more than enough to stop five-nines of people. Curiosity and spare time are not enough.<br>
<br>
I'll be happy to build up a reasonable "stump the geek" challenge for anyone that thinks I'm wrong on this.<br>
(And I'll be happy to learn something that could save my bacon someday, if I am.)<br>
<div class="im"><br>
----- Original Message -----<br>
> From: "chris fedde" <<a href="mailto:chris@fedde.us">chris@fedde.us</a>><br>
> To: "CLUE's mailing list" <<a href="mailto:clue@cluedenver.org">clue@cluedenver.org</a>><br>
> Sent: Wednesday, June 1, 2011 10:26:28 AM<br>
> Subject: Re: [clue] secure erase techniques?<br>
><br>
</div><div><div></div><div class="h5">> It might be a good idea to switch to /dev/zero. It is much faster<br>
> than /dev/random<br>
> You need to wait for it to finish to overwrite the whole disk. As a<br>
> least upper bound on the run time take the disk size and divide by<br>
> the<br>
> advertised transfer rate of the interface. 300Gbyte = 300*1024^3,<br>
> 3Mbyte/sec ideal SATA speed = 3*1024^2<br>
><br>
> using bc -l<br>
><br>
> (300*1024^3)/(3*1024^2)<br>
> 102400.00000000000000000000<br>
> ./3600<br>
> 28.44444444444444444444<br>
><br>
> about 29 hours if you really get full bandwidth from your sata port.<br>
> Chances are that's a gross under estimate.<br>
><br>
> Here is a quick device timing test:<br>
><br>
> [cfedde@home]$ dd if=/dev/urandom of=/dev/null bs=4096 count=1000<br>
> 1000+0 records in<br>
> 1000+0 records out<br>
> 4096000 bytes (4.1 MB) copied, 0.532551 seconds, 7.7 MB/s<br>
><br>
> [cfedde@home]$ dd if=/dev/zero of=/dev/null bs=4096 count=1000<br>
> 1000+0 records in<br>
> 1000+0 records out<br>
> 4096000 bytes (4.1 MB) copied, 0.001732 seconds, 2.4 GB/s<br>
><br>
> /dev/zero is much faster than /dev/urandom<br>
><br>
> On Wed, Jun 1, 2011 at 9:07 AM, Mike Bean <<a href="mailto:beandaemon@gmail.com">beandaemon@gmail.com</a>><br>
> wrote:<br>
> > No harm, no foul, it's not a particularly fast Celeron, so I don't<br>
> > mind<br>
> > letting it run long, I just wasn't sure what to expect.<br>
> ><br>
> > On Wed, Jun 1, 2011 at 8:15 AM, Will <<a href="mailto:will.sterling@gmail.com">will.sterling@gmail.com</a>><br>
> > wrote:<br>
> >><br>
> >> I should have recommended /dev/zero instead of /dev/urandom. For<br>
> >> your<br>
> >> purposes it would have been just as good and faster.<br>
> >><br>
> >> On Wed, Jun 1, 2011 at 8:02 AM, Will <<a href="mailto:will.sterling@gmail.com">will.sterling@gmail.com</a>><br>
> >> wrote:<br>
> >>><br>
> >>> It should eventually quit on its own. The amount of time it will<br>
> >>> take is<br>
> >>> dependent on how fast your CPU can generate random numbers and<br>
> >>> how large the<br>
> >>> partition is.<br>
> >>><br>
> >>> On Wed, Jun 1, 2011 at 5:09 AM, Mike Bean <<a href="mailto:beandaemon@gmail.com">beandaemon@gmail.com</a>><br>
> >>> wrote:<br>
> >>>><br>
> >>>> How long would I need to leave this running? cat /dev/urandom<br>
> >>>> ><br>
> >>>> /dev/sda1 's been going for long about 10 hours now. Is this<br>
> >>>> something that<br>
> >>>> I'll need to abort or does it terminate on its own?<br>
> >>>><br>
> >>>> On Tue, May 31, 2011 at 9:04 AM, chris fedde <<a href="mailto:chris@fedde.us">chris@fedde.us</a>><br>
> >>>> wrote:<br>
> >>>>><br>
> >>>>> Raymond,<br>
> >>>>><br>
> >>>>> What does the magic block size do?<br>
> >>>>><br>
> >>>>><br>
> >>>>> I'd go with two passes of "cat /dev/urandom > /dev/sdX" as<br>
> >>>>> root.<br>
> >>>>><br>
> >>>>> On Tue, May 31, 2011 at 8:51 AM, Raymond DeRoo<br>
> >>>>> <<a href="mailto:rderoo@deroo.net">rderoo@deroo.net</a>><br>
> >>>>> wrote:<br>
> >>>>> > Mike--<br>
> >>>>> ><br>
> >>>>> > In short, I'm giving one of my older PC's to a friend's<br>
> >>>>> > friend. One<br>
> >>>>> > of<br>
> >>>>> > those, I don't need it, things. In any case, in terms of<br>
> >>>>> > secure<br>
> >>>>> > destruction<br>
> >>>>> > of drives, my father's always taught me to disassemble the<br>
> >>>>> > drives and<br>
> >>>>> > throw<br>
> >>>>> > the heads and the platter out separately. Can't do it here,<br>
> >>>>> > they<br>
> >>>>> > need the<br>
> >>>>> > drives, so I thought I'd ask for advice in case we have<br>
> >>>>> > members who<br>
> >>>>> > might<br>
> >>>>> > know a thing or two about this sort of thing. I figured I'd<br>
> >>>>> > probably<br>
> >>>>> > just<br>
> >>>>> > boot it to a live CD and nuke the partitions, and that's<br>
> >>>>> > probably<br>
> >>>>> > enough,<br>
> >>>>> > after all, I don't need like a military-grade erase, but I'll<br>
> >>>>> > settle<br>
> >>>>> > for<br>
> >>>>> > making it @#$@#$@$ hard to recover. Any suggestions are<br>
> >>>>> > welcome.<br>
> >>>>> ><br>
> >>>>> ><br>
> >>>>> > # dd if=/dev/urandom of=/dev/sda bs=387 count=<size of disk<br>
> >>>>> > in bites><br>
> >>>>> > / 383<br>
> >>>>> > Recover from this *IS* still possible, but generally requires<br>
> >>>>> > someone<br>
> >>>>> > who is<br>
> >>>>> > *VERY* knowledge about drives to do as such.<br>
> >>>>> > .r<br>
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