wiping out data for server decommission
Hi all,
I have a task to wipe out all the data in a server that is about to be de-commissioned. I came up with the idea of * identifying the Volume group information from bdf output * Use vgdisplay -v to find out disks under root volume group * Use 'dd' command to wipe out the information on the disks (nohup dd if=/dev/zero of=/dev/rdsk/${DISK} bs=8192k &) Would like to take advise as to, is this a right approach or are there any better methods to achieve this task? Thank you in advance! |
You could boot from a livecd and then dd /dev/zero the whole of the disk.
Within our company the policy is to have the drives physically destroyed after use, basically a company turns up with a van and shreds the HD on-site. The whole "must over-write X times with zeros or random values" thing is pretty sensationalist, once with 0's is enough to deter anyone except those with access to tunnelling electron microscopes to try and reconstruct data. |
On a couple of occasions I've just used mkfs.ntfs. Unless you force a quick format, it'll zero out every block after formatting the metadata.
Nice and convenient, but no quicker. EDIT: just noticed this is under "other *NIX" - I've only done this in Linux. |
Thanks for your suggestions TenTenths , syg00.
I will boot the server through a CD Image and write zeros on the whole disk. However, i have a question (that may sound silly). Isn't it possible to write the data directly from the Operating system shell. I understand that the command may not return back to prompt, as there wont be a tty to display the output. But would the following code run from memory and write zeros on all of the disk's sectors (or) would it stop as soon as it replaces the the data block that contains /dev/zero? Code:
dd if=/dev/zero of=<current root disk> |
you should not (try to) destroy the filesystem(s) containing the running os (this one will fail), all the others can be cleaned by that way.
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If you're SELLING them, I'd settle for nothing short of a sledgehammer and pound the hard drives into scrap. Anyone who buys them *COULD* (theoretically) still read the data from the drives...government agencies just have an easier time of it. You CAN recover good bits of data, even with the ones/zeros method. DBAN is MUCH harder, but experienced data forensics people can recover data. It's expensive, and the results may be hit or miss, but it can be done. It may sound paranoid, but you have NO IDEA what someone else will do, and if it's your company's data/client records, do you really want to take the chance? |
A sledgehammer is worse than zeroing the drive, because you can still recover info from the pieces. A PRNG that is not cryptographically secure is no better than zeroing the drive. If the data is "top secret" then use a cryptographic PRNG that is well seeded or encrypt the drive.
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The data density for HDDs is quite high, and please don't tell me that a sledgehammer will turn a HDD into sand ;)
http://www.xbitlabs.com/news/storage..._Analysts.html NOTE: values are in gigabits Let's say we currently have 100 GB / square inch, that equals about 0.15 GB / square mm, about a grain of sand or salt. So that grain of sand could contain a lot of data. Oh, and if you can turn a HDD into sand using a sledgehammer, please do post a video of it on youtube as that would be entertaining. |
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I would not be able to read data from HDD scraps, but using a microscope and sophisticated methods, one might be able to, just like one is able to see individual bits on a HDD platter. Of course, I'm referring to three letter agencies and not the layman, who would not have access to such methods.
I sense you are angry, maybe you should go out and pulverize a HDD to let off some steam. As for me, I've said what I wanted to say, and I'll go off to another thread. |
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And not angry a bit...but If you want to advocate against something, you should have proof of what you say. You don't. |
Thanks Everyone for participating and providing valuable insight.
I will take the suggestion to wipe out the hard disk as well as attempt to physically destroy them, if they are not going to be used in the same environment further. As of those disks which will be re-purposed in the same environment. I will go with zero-ing the whole disk (and fill it with random numbers. Thanks once again! |
There is some work on this subject that you should read:
At cmrr.ecu.edu, there is a Data Sanitization Tutorial (pdf). Amongst the highlights is a discussion of how some techniques of forensics and some of data destruction have become impractical over time and a discussion of various legal requirements and penalties that might exist under the different (US) applicable laws. this might concentrate the attention, in some circumstances. One particular issue that is easy to overlook is that of unused blocks in circumstances in which user accessible blocks are lower than native. In some cases, you might not be that worried about ancient data escaping the erasure process, but you probably shouldn't be that lax. There is also a discussion at SANS of the different microscopic techniques that can be used (and again, how progress has made this more difficult). Some other bits and pieces: http://www.nber.org/sys-admin/overwr...a-gutmann.html http://us.simsrecycling.com/Business...tion-Standards (probably better dealt with in the pdf at cmrr) https://en.wikipedia.org/wiki/Data_remanence https://www.anti-forensics.com/disk-...h-screenshots/ (And, of course, SSD erasure is different issue.) |
Nobody mentioned booting to a live cd and using "shred" here? Spend a couple days repeatedly writing random bits from /dev/urandom and then following with a final pass of zero's (so as to "cloak" the random passes a bit)?
I'm far from guru on this stuff but thought that should be pretty good. If not, please clue me in. |
Sorry about the delay in re-opening this thread, but a couple of points:
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Also, in the past week, I had chance to talk to people from DiskShred, who mechanically reduce disk drives to rubble. Now, I understand that this specific organisation is unlikely to be any use to you, and I am not recommending them over any other organisation with similar capabilities, but I just want to comment that their services are reasonably priced if you have a decent number of disks to go at. Otherwise, the price for a site visit does tend to make the price per disk a bit on the high side. The environmental aspects of reducing a disk to rubble are probably a bit irritating (that is, eliminating recycling, which seems undesirable, in general), but if it really was a high security project, and my job was on the line if it went wrong, I think that I'd want the mechanical destruction, at least as part of the process. |
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