Zeroing out a hard disk *Discussion*

[00010]

This page is to discuss the Zeroing of hard disks.

Here are some topics that I thought might be intresting.

1. Zeroing your hard disk, Is it healthy for your hard disk?

2. How "Securely" erased is your data when you Zero-out a hard disk?

3. Is it necessary at all to Zero-out a hard disk?


and anything else that has to do with hard drive Zeroing.

[lanceomni]

Simply partitioning a hard drive or any magnetic media should be sufficient in order to prevent issues when installing a new OS. I have heard of one or two people whom had issues with installing their bootloader on a freshly partitioned hard drive and zeroing it out corrected their problem. I have I have probably partitioned a drive for a new OS 1000 times on hundreds of different machines at home and at work and have never had any issues with a standard quick partition (removal of index)

Security
Now security is a different story. When you do a standard format you are just removing the index so all the actual files are still there. As long as that segment of the drive has not been overwritten with something new you should be able to retrieve the files with the proper recover software. Ive recovered 10 year old files from a computer that had at least 2 fresh installs. Id say thats kind of rare but the data is still basically intact until the drive has over written that spot.

I did a test one time and did a single pass zeroing out a drive and then tried to use recovery software. I wasnt able to recover anything. The US Department of Defense says magnetic media should be zeroed with 3-7 passes. There was also a paper written in the mid 90's by a guy named Peter Gutmann who said that a 35 pass method should be used. Now I don't know about anybody else but a single pass takes an eternity. Time is money and i am sure most people would agree that if you want to completely ensure that the contents of the drive have been securely erased you should physically destroy it and buy a new one.

If you are trying to keep your information safe from other people, simply taking a hammer or axe, which ever you prefer, and prevent it from ever being used again. If you are trying to keep it from the government or an extremely wealthy arch enemy than you may want to zero it a few passes, take it apart, expose it tostrong magnets, burn it and or pour some thermite on it.

Damage to drive
It will harm the drive as much as installing a program or downloading music.

[Imkantus]

There was also a paper written in the mid 90's by a guy named Peter Gutmann who said that a 35 pass method should be used. Now I don't know about anybody else but a single pass takes an eternity.

#!/bin/bash
mv lanceomni ~/bed
zaehler=0
while [ $zaehler -lt 34 ]; do
dd if=/dev/zero of=/dev/sdaX
let zaehler=zaehler+1
done

:D ;)

[00010]

I always do a 35x pass on every drive before a OS install or re-installation. but thats probably because I want the main computer I am using to be almost perfect, I dont want any problems down the road, I like a nice clean partition before I install, my 160GB hard drive takes 1 day and 8 hours to zero-out.

Heh..heh...Thermite.....

00010

[srs5694]

I'll add this: If the drive has been formatted using the GUID Partition Table (GPT) system, as most modern Mac drives are, then re-using it as a Master Boot Record (MBR) disk can result in a drive with contradictory MBR and GPT partition definitions, which can cause problems down the road. This is because the primary MBR partitions are all defined in the first sector of the disk. GPT uses a "protective MBR" in that location solely to keep MBR-only utilities from messing with the disk; the bulk of the GPT data occupy several sectors immediately after the MBR, with duplicates stored at the end of the disk. In an MBR disk, the sectors immediately following the MBR, as well as a few at the end of the disk, are usually unallocated. Thus, if you take a GPT disk and then repartition it with a GPT-unaware utility, the most important GPT data structures are likely to survive. This state of affairs could cause some utilities to become confused. In theory, you could end up wiping out your new MBR partitions if a disk utility uses the older GPT structures in preference to the MBR structures. (In theory, this shouldn't happen, but it might if the utility is poorly written or if you use it inappropriately.)

To avoid this problem, always completely destroy the GPT data structures. Apple's Disk Utility will do this when you tell it to create MBR partitions. GNU Parted (http://www.gnu.org/software/parted/index.shtml) will also do this when switching between label types with its mklabel command. My own GPT fdisk (http://www.rodsbooks.com/gdisk/) includes a couple of options that will do it -- one wipes out all GPT data and the other converts from GPT to MBR. I don't know what the various Windows partitioning tools do, offhand. Older tools, including Linux's fdisk and DOS's FDISK, are GPT-unaware and so can create a layout that's a ticking time bomb.

[00010]

I am doing a retail install now, zeroing the hard disk 35x pass 24 hours left.

Finally found all my kext files and trying to do a complete Retail install to get away from pre-patched.

00010