I prefer shred for erasing magnetic drives. dd can work too, but its options are arcane enough that it’s easy to make mistakes that lead to weird behavior.

If that doesn’t fix the unexpected size problem, I would suspect the USB bridge in your dock. Those things are notoriously buggy.

Connecting directly with SATA is a more reliable approach. It also lets you use hdparm to tell the drive to run a secure erase cycle on itself.

I mean, screwdriver to open and hammer for the platters works a charm, and is at least as secure as one pass of 0’s. Plus you can pull the magnets for whatever fun uses you can find later.

edit: Honestly even opening them and letting dust and other stuff in the air get on the platters pretty much destroys them… there’s a reason they are hermetically sealed.

I’d try to partition them in gparted. Write a couple different filesystems on them. If they are funky, just punch through them, as terribleplan said, with a hammer and screwdriver.

Maybe there weren’t enough power going to the drives, is it a powered dock? Otherwise if you don’t need the drives anymore the good’ol hammer always works.

By stops, you mean dd exits or hangs? Does dd throw an error/nonzero exit code? Anything in dmesg?

There’s no automatic mounting going on in the background, right?

Can you run dd with the “status=progress” option set to see what’s going on when it stalls? Also, how long until it stalls? In my experience, dd takes a really long time to write over an entire drive of that size, so you may just need to wait it out (could take a couple of days). You can also try increasing the block size (e.g., “bs=8m” or “bs=8M”, with the case of the “m” depending on your OS) and see if that helps to speed things along. Typically, the default dd block size (512 bytes) is pretty slow.

Note: I’m far from an expert but I have been using dd for similar applications as you for a few years. Hopefully something above can be of some help.

idk man, if there’s sensitive data on those drives i’d always err on the side of caution, there are much cheaper ways of doing secure data deletion, you can dismantle a drive with a screwdriver, or core them with a drill (my old worksplace had a hydraulic press they ran batches of drives through)

if you wanted something less intrusive there are bootable images like DBAN (Darik’s Boot and Nuke) that handle secure erasure pretty well, you can enforce multiple passes, and even connect multiple drives at once

if the data isn’t that sensitive I always like trying to unpartition/repartion the drive, then see if you can use dd to fill the drive with zeros/random data

Sometimes this is due to buggy UAS support. Look into blocking it globally or for your specific dock but check your logs first ideally.

That sounds fine, but what is the actually did command you are running? A simple dd if=/dev/zero of=/dev/sdf bs=1m should be all you need. If you are using dd, run iotop or something similar in the background to see if there’s any writing actually happen.

When you say dd “stops” does it just quit? If so it might be the dock briefly disconnecting, you should be able to see this happen by watching dmesg with dmesg -w as you are running your dd command.

Use the shred command instead. See https://www.freecodecamp.org/news/securely-erasing-a-disk-and-file-using-linux-command-shred/ for options on how to use it, for drives it’s a bit further down.

Depending on the sensitivity of the data on the drives I would always suggest a “professional” shredding service that destroys the physical disk as well.

Try mounting them. What is the dd command you’re using?

Now, depending on your threat model maybe a drill and a sledgehammer will be enough. If your threat model is rather high and it is really sensitive data, I would still professionally destroy them even after writing zeros.

It seems unlikely EVERY drive is bad in the exact same way. My money is on either the adapter having an issue (check dmesg for any usb errors?) or your USB port being marginal on providing enough power to run it, if it’s a bus-powered adapter.

Those really suck for mechanical drives and I’ve NEVER had good luck if that’s the case.

Are you getting any errors in your system log?

The first thing I would suspect is the USB dock. Do you have a computer with a spare SATA port or an eSATA dock that you could try erasing a drive in?

Are all my drives bad?

It seems more likely that your usb adapter is at fault here …

You could just take the platters out. I use mine a fancy coasters.