How to Wipe Clean A HD. Really Clean!

[nujinini]

Hello!

I have an old IDE HD (80G) w/c I have recovered some family photos & some music files from using Parted Magic. I used an IDE/SATA to USB cable. It was the first time I did such and was surprised to see that aside form the pictures and mp3s, my old personal & business files still can be recovered even after deleting and even reformatting said HD.

I will be putting this HD back to the old laptop and send to the shop for some minor repairs and eventually give it to a friend.

May I please ask on how to wipe/shred/overwrite the HD so as to totally make it impossible to recover anything from it? Like sort of how to make it really clean. I read in this forums about "dd" but am not yet familiar with it.

Thanks guys!

[jun@localhost ~]$ sudo fdisk -l
[sudo] password for jun: 

Disk /dev/sda: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xc5e3f820

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        1555    12490506    7  HPFS/NTFS
/dev/sda2            1556       15817   114559515    5  Extended
/dev/sda3           15818       30401   117145980    7  HPFS/NTFS
/dev/sda5            1556        4768    25808391   83  Linux
/dev/sda6            4769        5558     6345643+  82  Linux swap / Solaris
/dev/sda7            9380       10144     6144831   83  Linux
/dev/sda8            6731        8285    12490506   83  Linux
/dev/sda9            5559        6730     9414058+  83  Linux
/dev/sda10           8286        9379     8787523+  83  Linux
/dev/sda11          10145       15817    45568341   83  Linux

Partition table entries are not in disk order

Disk /dev/sdb: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xa282a282

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        9553    76734441    6  FAT16
/dev/sdb2            9554        9729     1413720    5  Extended
/dev/sdb5            9554        9729     1413688+   6  FAT16
[jun@localhost ~]$

[Irithori]

Word of warning:
Both, dd and badblocks, will start their work immediately and without warning.
The fdisk -l you have posted, indicates that sdb is the disk you want to delete.
But please verify that before.

With dd:

dd if=/dev/zero of=/dev/sdb bs=1M

or

dd if=/dev/urandom of=/dev/sdb bs=1M

The 2nd uses pseudo random data for the extra paranoid


I do use badblocks for checking drives health.
But it works for secure disk wiping, too.

This will write the entire disk 4 times with these patterns: 11,10,01,00
I really doubt, that anything is left to recover after that, even for professional data rescue services.

badblocks -svw /dev/sdb

[nujinini]

Word of warning:
Both, dd and badblocks, will start their work immediately and without warning.
The fdisk -l you have posted, indicates that sdb is the disk you want to delete.
But please verify that before.

Hi! Thank you so much!

So to heed the warning? Can I please ask if this is correct?

I execute any or both of these in the terminal as #:

dd if=/dev/zero of=/dev/sdb bs=1M
dd if=/dev/urandom of=/dev/sdb bs=1M

And its not yet going to erase anything right?

[Irithori]

Both dd commands *will* erase the disk sdb.

They overwrite it from the first block up to the last, only with different "data".
Hex zeros in the first dd, and pseudo random data in the second.

It takes a while to go through the whole disk, so the later blocks are not immediately erased.
But after dd completed, there will be no more useable data on it.

[oz]

May I please ask on how to wipe/shred/overwrite the HD so as to totally make it impossible to recover anything from it? Like sort of how to make it really clean.

I'm not sure that it will ever be totally impossible to retrieve files from an existing hard drive but you can check out Darik's Boot and Nuke (DBAN) for a good shredder:

Darik's Boot And Nuke | Hard Drive Disk Wipe and Data Clearing