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Thread: Securely earsing your harddrive the hard way

  1. #41
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    Default Re: Securely earsing your harddrive the hard way

    Ok, this should be my final correction. I added another command that might be useful.
    Hopefully it will be useful to everyone.
    +++ ATH0

    . . . . . . . .
    LOGOFF COMPLETE

  2. #42
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    Default Re: Securely earsing your harddrive the hard way

    Quote Originally Posted by robin_listas View Post
    On 2011-06-01 00:36, JoergJaeger wrote:
    >
    > Hi, what do you think about this version. Is this better? I can not make
    > everyone happy, but i am trying too.
    >
    > Thanks for the input. If its good, maybe vote on it. If there are any
    > grammatical errors, correction is appreciated.



    The device /dev/0xFF does not exist. Maybe it has another name.

    And then, there is another method, provided by the firmware of the
    harddisk. I think it is fired by "hdparm --security-erase". I have never
    used it, see the manual first.

    --
    Cheers / Saludos,

    Carlos E. R.
    (from 11.2 x86_64 "Emerald" at Telcontar)
    Gee, i have seen this too late. Ok, i have to dig again. Thanks for the info.
    +++ ATH0

    . . . . . . . .
    LOGOFF COMPLETE

  3. #43
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    Default Re: Securely earsing your harddrive the hard way

    I want to start this FAQ with the opening that there is no 100% solution.

    To a certain degree any information may be obtained, but you can limit this a great deal.
    Also, this is a guide for home users and does not apply to business or professional needs. Keep in mind that this solution assumes that you write over the whole disk and not just a partition.

    Since we deal for the most part with newer drives, it should work pretty well. Of course there may be tools out there, that may retrieve information, but the chances are slim. Just my assumption.
    I will list several option you can use and you may pick one over the other. The choice is yours.

    Attention:
    Keep in mind that you will erase all data on the hard-drive. So before doing anything make a backup or simply copy the data to another drive.

    Make sure you know what you are doing since i will not take any responsibilities!



    Preparation:

    First you want to know what the name of the drive is you want to erase.
    You need to use the following command.

    Open your terminal and enter (you need to be root, so su first).

    Code:
    fdisk -l
    You do this to find your hard-drive, the one you want to erase.

    It should looks like this.

    linux-ia48:/home/yourname # fdisk -l
    Disk /dev/sda: 500.1 GB, 500107862016 bytes
    255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x5d8c637e

    Device Boot Start End Blocks Id System
    /dev/sda1 63 198643786 99321862 7 HPFS/NTFS/exFAT
    /dev/sda2 311965696 976773119 332403712 f W95 Ext'd (LBA)
    /dev/sda3 303581184 311965695 4192256 82 Linux swap / Solaris
    /dev/sda4 * 198660096 240670719 21005312 83 Linux
    /dev/sda5 311967744 376948735 32490496 83 Linux
    /dev/sda6 376950784 976752639 299900928 83 Linux

    Partition table entries are not in disk order

    Disk /dev/sdb: 2000.4 GB, 2000398934016 bytes
    255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x000c4672

    Device Boot Start End Blocks Id System
    /dev/sdb1 2048 3907028991 1953513472 83 Linux

    Disk /dev/sdc: 160.0 GB, 160041885696 bytes
    256 heads, 63 sectors/track, 19381 cylinders, total 312581808 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0xa8a8a8a8

    Device Boot Start End Blocks Id System
    /dev/sdc1 * 2016 312578783 156288384 a5 FreeBSD

    In my example we will erase the very last hard-drive named FreeBSD which is a device sdc1.
    You may want to write the name of the hard-drive down just not to forget in your real life.
    We will use /dev/sdc1 as an example. You will put your hard-drive name instead of the name in the example.


    Method 1:


    Now, after we know the hard-drive, and you sure about it, you only need to enter this command.

    Code:
    dd if=/dev/zero of=/dev/sdc1
    dd will duplicate and copy onto sdc1, thus erasing every single bit.
    Also, this method will take time. In fact a lot of time. I did it with a 160GB HD and it took about 3 hours. So, depending on the size of your drive you may want to let it run till its done and go out or do some shopping, reading or whatever you feel like.
    p.s. If you want to be double sure you can mix method 2 with 1. That way you randomly write first and last zero it.
    Method 2:

    The other method will override the drive in a random fashion.

    Code:
    dd if=/dev/urandom of=/dev/sdc1
    Also another possibility is

    Code:
    dd if=/dev/urandom of=/dev/sdc1 conv=noerror
    This will write random values. The value conv=noerror will also prevent an exit of the command due to an error on the hard-drive. Keep in mind that this method will take a VERY long time, so its perhaps best done on a weekend or if you are on vacation.

    Hint:
    The 'conv=noerror' variable can be used with any of the other dd command.


    Method 3:


    If shred is installed, you can use this command.

    Code:
    shred /dev/sdc1
    Method 4:

    There is also yet another choice > hdparm. This is a more problematic choice if not done carefully. So reading the man page is required.
    Here is the link to it. HDPARM


    Conclusion:


    This should cover most methods i am aware off. If there are any others, please post them.
    After long hours of doing this, your drive should be wiped off any data you had previously. There may be always methods to retrieve data so in case you are really worried, discard all of the above and simple shred the hard-drive in a hardware shredder. See your local electronic junkyard for that option.

    Here is some further reading suggestion for you.

    Secure Erasing A Hard-Drive

    P.s. if you feel to comment or add to this FAQ, please do so since i do it to the best of my knowledge and it may not complete.

    Since this is not just my doing, I like to mention the people that made it possible.
    Thanks to robin listas, skaterich & nrickert and everyone who contributed some ideas and suggestions.
    +++ ATH0

    . . . . . . . .
    LOGOFF COMPLETE

  4. #44
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    Default Re: Securely earsing your harddrive the hard way

    Quote Originally Posted by robin_listas View Post
    On 2011-06-01 00:36, JoergJaeger wrote:
    >
    > Hi, what do you think about this version. Is this better? I can not make
    > everyone happy, but i am trying too.
    >
    > Thanks for the input. If its good, maybe vote on it. If there are any
    > grammatical errors, correction is appreciated.



    The device /dev/0xFF does not exist. Maybe it has another name.

    And then, there is another method, provided by the firmware of the
    harddisk. I think it is fired by "hdparm --security-erase". I have never
    used it, see the manual first.

    --
    Cheers / Saludos,

    Carlos E. R.
    (from 11.2 x86_64 "Emerald" at Telcontar)
    I could not confirm it either, so i just took it out. But i included your suggestion. Haven't tried it myself.
    +++ ATH0

    . . . . . . . .
    LOGOFF COMPLETE

  5. #45
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    Default Re: Securely earsing your harddrive the hard way

    On Wed, 01 Jun 2011 01:06:04 +0000, JoergJaeger wrote:

    > I want to start this FAQ with the opening that there is no 100%
    > solution.


    Well, there is, but it involves physical destruction of the drive, which
    kinda limits reuse. Most electronics recycling places can securely
    destroy a drive by grinding it into dust. I've done that with personal
    drives that had personal information on them that I didn't want recovered.

    Jim

    --
    Jim Henderson
    openSUSE Forums Administrator
    Forum Use Terms & Conditions at http://tinyurl.com/openSUSE-T-C

  6. #46
    Will Honea NNTP User

    Default Re: Securely earsing your harddrive the hard way

    Jim Henderson wrote:

    > I've observed that as well, I'm sure we could swap stories sometime over
    > our beverage of choice.


    Call that an appointment if you ever get in the Colorado neighborhood.
    Sadly, my travel has been increasingly driven by funerals in recent years so
    I don't make the rounds as in days of yore. And I'm sure Denver D will
    appreciate my aprehension regarding air travel - that pilot could have been
    one of my washed out students!

    --
    Will Honea

  7. #47
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    Default Re: Securely earsing your harddrive the hard way

    On Wed, 01 Jun 2011 03:23:07 +0000, Will Honea wrote:

    > Jim Henderson wrote:
    >
    >> I've observed that as well, I'm sure we could swap stories sometime
    >> over our beverage of choice.

    >
    > Call that an appointment if you ever get in the Colorado neighborhood.
    > Sadly, my travel has been increasingly driven by funerals in recent
    > years so I don't make the rounds as in days of yore. And I'm sure Denver
    > D will appreciate my aprehension regarding air travel - that pilot could
    > have been one of my washed out students!


    You bet. I have had occasion to travel to Colorado, though with the
    job changing, who knows where I'll end up traveling to.

    Jim



    --
    Jim Henderson
    openSUSE Forums Administrator
    Forum Use Terms & Conditions at http://tinyurl.com/openSUSE-T-C

  8. #48
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    Default Re: Securely earsing your harddrive the hard way

    On 06/01/2011 05:23 AM, Will Honea wrote:
    > that pilot could have been one of my washed out students!
    >


    no doubt! and, i washed out some real losers! fortunately most will soon
    reach mandatory retirement, and anyway if they are still alive they
    probably finally learned what to look at when.

    --
    dd CAVEAT: http://is.gd/bpoMD
    [NNTP via openSUSE 11.4 [2.6.37.6-0.5] + KDE 4.6.0 + Thunderbird 3.1.10]
    Dual booting with Sluggish Loser7 on Acer Aspire One D255

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