Em 12/07/2015 10:03, "Mick" <michaelkintz...@gmail.com> escreveu: > > On Sunday 12 Jul 2015 13:35:25 Marc Joliet wrote: > > Hi, > > > > I have to failed drives that I want to give away for recycling purposes, > > but want to be sure to properly clear them first. They used be part of a > > btrfs RAID10 array, but needed to be replaced (with "btrfs replace"). (In > > the meantime I converted the array to RAID1 with only two drives.) > > > > My question is how precisely the disks should be cleared. From various > > sources I know that overwriting them with random data a few times is > > enough to render old versions of data unreadable. I'm guessing 3 times > > ought to be enough, but maybe even that small amount is overly paranoid > > these days? > > > > As to the actual command, I would suspect something like "dd > > if=/dev/urandom of=/dev/sdx bs=4096" should suffice, and according to > > https://wiki.archlinux.org/index.php/Random_number_generation#.2Fdev.2Furan > > dom, /dev/urandom ought to be random enough for this task. Or are cat/cp > > that much faster? > > > > Any thoughts? > > > > Greetings > > I use urandom a couple of times (3 to 5), because random takes too long and I > don't store state secrets on my disks. Then I dd onto it a final round of > /dev/zero. Finally, run hdparm to securely erase it for good measure.[1] All > of this could be an overkill, but do it out of habit these days. > > It is worth saying that I use haveged to increase entropy: > > [I] sys-apps/haveged > Available versions: > 1.5 > ~ 1.7a > 1.7a-r1 > ~ 1.9.1 > Installed versions: 1.7a-r1(12:46:23 04/21/14) > Homepage: http://www.issihosts.com/haveged/ > Description: A simple entropy daemon using the HAVEGE algorithm > > I should clarify that disks which contained financial data are dealth with a > high speed angle grinder, after I remove the outer casing of the drive and don > a pair of goggles.[2] *Only then* do I recycle the bits left. ;-) > > > [1] https://ata.wiki.kernel.org/index.php/ATA_Secure_Erase > > [2] You can also use a hammer, a drill, or any similar implement which will > completely break the physical disk platters to bits. > > -- > Regards, > Mick
A physical damage is what I guess be the best choice for sensitive data. I use to disassemble the HDD and rub a strong magnet over the disks' surfaces. Just my 2c. Best regards, Francisco
