Wiping hard drive for resale.
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  1. #1
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    Wiping hard drive for resale.

    I use the following dd command to wipe hard drives:
    Code:
    dd if=/dev/zero of=/dev/sdX bs=1M
    However, I may want to sell some of these 250GB HDDs, is the dd operation described above sufficient to protect against any "prying eyes" a buyer might have?
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  2. #2
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    Re: Wiping hard drive for resale.

    You should add a count option

    dd if=/dev/zero of=/dev/sdX bs=10M count=1000 #or some larger count value
    Leslie in Montreal

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  3. #3
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    Re: Wiping hard drive for resale.

    There are a number of ways to go after secure and irreversible deletion of files.

    Take a look at the article from Network World "Shredding files in Linux"

    If you wanted to be absolutely paranoid about the contents of a drive, you could use one of the methods in the article to walk the file tree and shred all the files, then go for the
    Code:
    dd if=/dev/zero of=/dev/sdX bs=10M count=1000 #or some larger count value
    Cheers!
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  4. #4
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    Re: Wiping hard drive for resale.

    Thanks lsatenstein, I'm running
    Code:
    dd if=/dev/zero of=/dev/sdX bs=10M count=1000
    right now on the first of 5 250GB WD HDDs I'm taking out of service.

    @jims, thanks for the link, I forgot that 'wipe" only works on magnetic media, not hard disks.

    I am running a live session of Ubuntu 16.04(Mate) from a USB drive, I noticed an application in the menu called "Disks", basically gnome-disk-utility. How well does that work?
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  5. #5
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    Re: Wiping hard drive for resale.

    Quote Originally Posted by lsatenstein
    You should add a count option

    dd if=/dev/zero of=/dev/sdX bs=10M count=1000 #or some larger count value

    I don't think you understand what count is doing here. count is the number of records of (bs) size that are transfered. It means that for a bs=10M block it would copy /dev/zero to the first 10GB of the destination device.

    As for reselling drives: data is generally forensically recoverable from hard disks even with multiple random pattern overwrites. If there is nothing confidential on them then I suppose it doesn't matter.

  6. #6
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    Re: Wiping hard drive for resale.

    I forgot about Dban(Darik's Boot and Nuke), used it back in the early 2000s. It's a live Linux environment:

    The most recent version of DBAN is 2.30, which was released on 4 June 2015. Since that time DBAN development seems to have ended and the official website used by Blancco to market their Blancco Drive Eraser instead.

    There is an unofficial fork of DBAN that is actively maintained. The dwipe program that DBAN uses has been forked and is available as a standalone command line program called Nwipe, which is actively maintained. Nwipe has been incorporated in free software rescue toolkit packages, such as the All in One - System Rescue Toolkit.
    I'll burn the 15MB .iso to a CD and try Dban on one of the HDDs. Am currently doing
    Code:
    dd if=/dev/urandom of=/dev/hdx
    which is taking quite a while.
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  7. #7
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    Re: Wiping hard drive for resale.

    I doubt that it would be worth trying to sell these drives, I checked my purchase history and found the newest of the five is over 8 years old; the oldest one is over 10. if I sold them on ebay I'd have to pay selling fees, Paypal fees and probably spring for free shipping. All that for what likely would be a $10 sale.

    I'm helping my neighbor across the road learn Linux, maybe I'll install some different distros on the drives and give them to him to play with.
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  8. #8
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    Re: Wiping hard drive for resale.

    Quote Originally Posted by hrsetrdr
    ... I noticed an application in the menu called "Disks", basically gnome-disk-utility. How well does that work?
    It works reasonably well, but then again, I tend to accomplish most things using CLI
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  9. #9
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    Re: Wiping hard drive for resale.

    Quote Originally Posted by tempest766
    I don't think you understand what count is doing here. count is the number of records of (bs) size that are transfered. It means that for a bs=10M block it would copy /dev/zero to the first 10GB of the destination device.

    As for reselling drives: data is generally forensically recoverable from hard disks even with multiple random pattern overwrites. If there is nothing confidential on them then I suppose it doesn't matter.
    Exactly, count is unnecessary and even not wanted here because the entire drive needs to be overwritten.

    It seems the only way to destroy data entirely is to shred the drive into pieces, this type of recoveries are rather expensive and time consuming, the data value would need justify it. In general overwritting the drive with random patterns a couple of times is preferable approach.

  10. #10
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    Re: Wiping hard drive for resale.

    I read a piece by a government security employee who said none of the ways to wipe and shred a HDD are 100% effective. He added "Never sell a used HDD unless you melt it down to a puddle first." But of course it's his job to be super paranoid.
    I live in my own little world, but it's OK, they know me here.

  11. #11
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    Re: Wiping hard drive for resale.

    and that includes the US Department of defence algorithm offered by HDD wiping many programs. How much you want to trust them is up to you but I prefer destroying old drives once they are run to the point of failing.

    I'm not sure what you are expecting to make back from selling used 250GB drives that are without warranty ticking time bombs for anyone who buys them, they are so cheap new that I certainly wouldn't risk second hand.

  12. #12
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    Re: Wiping hard drive for resale.

    Quote Originally Posted by antikythera
    I'm not sure what you are expecting to make back from selling used 250GB drives that are without warranty ticking time bombs for anyone who buys them, they are so cheap new that I certainly wouldn't risk second hand.
    Exactly, not worth the hassle or risk, I did offer them to my neighbor but he declined. It might be fun and educational to explore some recovery software, just to see how well the discs were actually wiped.
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  13. #13
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    Re: Wiping hard drive for resale.

    I suspect you will no be able to read anything with the drive if you rewrote all the bits. However, it is supposedly possible to read the from the erased plates by other means which involves disassembling the drive and reading directly from the plates.

  14. #14
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    Re: Wiping hard drive for resale.

    Quote Originally Posted by srakitnican
    I suspect you will no be able to read anything with the drive if you rewrote all the bits. However, it is supposedly possible to read the from the erased plates by other means which involves disassembling the drive and reading directly from the plates.
    Well if that's the case I should be able to just toss the drives in the trash, I've not done anything to spark interest of the NSA.

    I'll probably keep the HDDs for spares, or in case someone I know needs a drive.
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  15. #15
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    Re: Wiping hard drive for resale.

    Quote Originally Posted by srakitnican
    I suspect you will no be able to read anything with the drive if you rewrote all the bits. However, it is supposedly possible to read the from the erased plates by other means which involves disassembling the drive and reading directly from the plates.
    For the common user a program like "wipe" or secure-erase is adequate, but yes, there are methods for recontructing the erased data from the platters after they have been dissassembled. Too involved to go into details, but the FBI forensic labs are perfectly capable of it, with better success than you might think possible.

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