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dd if=/dev/zero of=/dev/hda bs=1k count=1kA dd command is easier to type, and avoids any OS except Puppy.Sage wrote:I gave a simple debug script recently that has the effect of wiping the entire HD.
Have you tested this? Have you read the academic papers on this subject? Please, use DBAN, not your own idea of what might be good enough, for any truly sensitive data. The standards (DOD 5220.22-M, RCMP TSSIT OPS-II, and so forth) for disk wiping exist for a reason. Recovering data from HDs is a whole specialist field all to itself... http://www.digitalissues.co.uk/html/os/misc/shred.html is a very gentle introduction, with links to several of the well known articles on this.Since the FS is radically different in each case, it would take someone like the CIA to make something out of any remaining fragments.
Sage wrote:snip
Since the FS is radically different in each case, it would take someone like the CIA to make something out of any remaining fragments.
Just check out:Yes, I think we're wasting our time here. The original post was very ambiguous and Max has yet to post again, so it's probably best if we just leave this until he comes back with some useful information.noip wrote:Whilst I've found the discussion on wiping / cleaning / zeroing the HDD interesting, and have been taking notes, I read the original request as one to manipulate the partitions on the disk (even though the term "wipe" was used). I thought the aim was just to eliminate a small ntfs partition.... ??
Just a thought ...
GS
ftgs
Well, I responded in part:noip wrote:Whilst I've found the discussion on wiping / cleaning / zeroing the HDD interesting, and have been taking notes, I read the original request as one to manipulate the partitions on the disk (even though the term "wipe" was used). I thought the aim was just to eliminate a small ntfs partition.... ??
I think that seems to fit your interpretation of the original post fairly well? As someone else pointed out, the initial question was not especially clearly defined. Hopefuly we'll hear back from the person who asked it with more information.jmarsden wrote:If you only want to zero one partition, replace of=/dev/hda with of=/dev/hdaX where X is a number between 1 and 4 representing the partition to be wiped. Then reset its type with fdisk, create an ext3 or whatever filesystem on it, and off you go.
My understanding is that such tools generally use a single wipe approach, often to all zeroes. If so, how (in what way) are they any "better" than dd if=/dev/zero ? If they really do something different, what is it that they do -- it would be good to know, so we can improve DBAN and shred and related tools along similar lines. Comparing the single-wipe-to-zeroes approach with the DOD and RCMP standards already referenced, unless the tools you refer to are doing something truly extraordinary, I must disagree with your (or Max's?) definition of "best".rarsa wrote:The best way to clean up an HDD is to use the HDD manufacturer's tools.
Every HDD manufacturer provide tools to completelly wipeout the HDD in a way that the only way would be to detect residual magnetic ghosting.
Not really. If an OS writes your data to sectors on the drive using a defined interface, it can zero them, or write random stuff over them, in the same way, to scrub the drive. The drive can'ttell the difference between a request to write zzeros to sector X during a scrub operation, and a request to do so during normalOS operation. So where physically that data is on the platters makes no difference.Flash wrote:I'm certainly no expert in hard drives, but according to this, the way modern hard drives work, you cannot directly control the position of the read/write head. Instead, there is a controller inside the hard drive which "maps" addresses, and interprets and executes the commands sent by the OS. Is it conceivable that this controller might do things in a proprietary way, making the manufacturer's tools the best for the job?
As far as I know your understanding is the same as mine.jmarsden wrote:My understanding is that such tools generally use a single wipe approach, often to all zeroes. If so, how (in what way) are they any "better" than dd if=/dev/zero ?
Apparently you missed what else I wrote? Later in the same post, I said:rarsa wrote:The command you posted only writes zeroes to the first 1 MB. That would be enough to clean the partition table and MBR. If you know your HDD precise geometry I guess that dd could be used to completelly wipe it out.
You don't need the disk geometry, it just writes zeroes until it can't do so any more -- i.e. the end of the disk is reached. It is arguable for that purpose one should use bs=512 so it writes one sector at a time rather than two, I suppose -- otherwise theoretically you might leave the final sector of a disk that has an odd total number of sectors unwiped.jmarsden wrote:You can zero out the entire disk by omitting the count= parameter completely, if you wish.
I think you misunderstand. dd isn't better, it's just more general, and I can read and edit its source code should the need arise. So I trust it to perform as advertised far more than I trust binary executables from a vendor. (Also, I much prefer learning one tool than learning 4 or 5 for the same purpose). And having learned to use dd, that knowledge will be useful in many other circumstances than just low level hard drive wiping (creating floppy, zip, CD-R, USB key etc. image files, cuting files into smaller pieces for transport over say email links, ... plenty of tasks dd can do with ease, that the vendor tools can't). dd is available in Linux, *BSD, OS/X, most commercial Unix variants, and even Windows (via Cygwin), so again, having learned one tool, that knowledge remains applicable as one moves among a variety of OS environments and hardware platforms (do the vendor tools work on a Mac? On a Sun workstation? Will they wipe a bunch of SCSI disks connected via some proprietary RAID controller?).rarsa wrote:If you find dd better good. My opinion is that the tools provided by the vendor are easier to use and are sure to work OK with your HDD.
