A Qnap NAS has a drive with some bad sectors, I want to RMA it, but before just want to figure out how to prepare a drive? It’s part of a raid 5 setup of 4 drives unencrypted. So I want to remove it and wipe it. Got a Linux machine I can use, but never done this before.
What are common Linux tools to do that sensibly?
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I like badblocks in destructive mode. It can also do multiple rounds of overwriting. It is also a good tool to burn in a new hdd or test a used one. just check smartctl bad sector count, run it, check again if it increased.
dd if=/dev/zero of=/dev/disk
I’d recommend /dev/urandom instead of /dev/zero
Use shred , it will automate multiple random passes, and finish with a zero pass.
Yeh, you’re right
no help to you, but a heads-up to anybody yet to deploy disks in such a scenario: always use encryption by way of LUKS2. you can set it up easily to unlock it on boot by a key file on the boot drive, thumb drive, TPM and such. so when a drive gets sold, RMA’d, etc., you got none of these issues.
source: sold my old drives recently and the shred procedure took ages. the new ones are encrypted so none of that shit no more.
shredor alternatively you can zero out all the bytes in a drive withdd if=/dev/zero of=/dev/<DRIVE>shredCan also be used from KDE Partition Manager.
Use LUKS encryption in the future.
When I sold my drives, I used veracrypt with a 128 character password and PIM of 800+.
Isn’t that the same thing as shredding?
No.
Can you elaborate?
Installing an operating system and enabling encryption won’t overwrite the data on the entire disk. Instead, it will only overwrite on the specific sectors on which this operating system was installed.
Other “previous” data on the disk will remain intact and unaffected.
I understand what you mean. The way I did it was a full disk encryption as an “external drive” so the whole disk was encrypted
Unless the OS installer chooses to wipe the driver, which Debian’s (non-calamares) installer does.
The day job is Private Possum territory, so our agreement is
- we won’t send in drives
- we will send proof of destruction
and I’m sure it costs more, but we don’t have to worry about recovered user data.
Our stuff is also in those crazy-secure datacenters, too, so we don’t need to mess with crypto-at-rest.
If the drive has bad sectors that it can’t read right now, it likely had other sectors that were marginal and got copied (remapped) to new spare sectors before they became unreadable. So there is still potentially recoverable data in the remapped sectors, and not much you can do about it.
Basically, writing zeros to the disk is about as good as you can hope for. If your data is s00per seekrit to the point where you can’t stand the possibility of any bits at all being recovered, you basically have to melt the drive. Otherwise, zero it and send it in.
Next time, set up encryption ahead of time, so your new drives never see plaintext. Some drives have a “secure erase” feature that is basically a crappy version of this built into the drive.
Assuming the drive writes normally a simple command like
dd if=/dev/random of=/dev/sdX
Where sdX is the location of the drive should do the trick. Depending on drive time this may take a bit.
Always use /dev/urandom for this purposes. /dev/random will be locked if it doesn’t have enough entropy. It is good for getting some random kilobytes for cryptography but not 2 TB of random data for disk wipe.
Yeah my first thought was just keep running dd commands, and sooner or later you’ll have the hdd wiped.
Instructions unclear, accidentally deleted 200 EB of irrecoverable NASA data.
Just keep in mind that you can’t wipe the bad sectors that have been remapped. That’s unlikely to be an issue for a personal drive, but something to consider if it held particularly sensitive information.
Sectors are what, 4kb? The odds of something sensitive being in those each of those 4kb is low (but never zero).
If the drive implements the ATA secure erase command properly, it should also clear all the remapped sectors too. But I don’t know if I trust them to implement it properly. Maybe try it and inspect the disk with a hex editor.
dd if=/dev/zero of=/dev/sdX bs=1M
This command is much faster. Instead of random bits, it just marks everything zero (dude). Is good enough.
DNAM. Is or used to be on the UBCD.
For the future remember, encryption helps when the disk is no longer operational.
