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 to the computer 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.

Could be a bad dock or usb controller, try a different one. Otherwise just snap the sata connector off, and most people will not bother to get anything off.

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.

add with status=progress would be a good idea lace to start as the other commenter mentioned. Htop has a configuration in settings that will allow you to see disk writes as well.

There are also other options such as shred you can use.

using dd to zero a drive - is not a secure way to delete the data. It could potentially be recovered.

You mount filesystems, but you are accessing the device directly, so you are not using the filesystem, so no need to mount.

As the other comment mentions, it sounds like a controler issue. monitor the output of sudo dmesg -w as you are doing the work on them.

need to have them “professionally” destroyed at about $25 a drive.

A Hammer is about $5 and will destroy them. :)

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

I would suspect the cabling and/or the dock before all your drives.

Writing zeros to hard disk does not securely delete the contents. https://en.wikipedia.org/wiki/Gutmann_method

A further problem with writing zeros to the contents to /dev/sdf/ is that contents of any relocated sectors will not be over-written. It might be possible to recover data from those bad sectors.

If you can get the dock working, look at using hpparm to do SATA secure delete? It has flags to support this. https://www.putorius.net/securely-erase-a-sata-hard-drive-hdparm-linux.html You could then use hpparm to set an unique, LONG, random password on each drive.

Are you using /dev/zero as the input for dd, such as dd if=/dev/zero of=/dev/<HD to erase>? This is how I used to do this but I’ve recently switched to using the little tool ‘nwipe’ which allows to wipe multiple drives in parallel and show proper progress.

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.

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.

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.

Are all my drives bad?

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

I imagine that you’re filling the disk cache with the zeros and then it takes a while to actually write that to the disk - so be patient.

Have you tried securely erasing the disks using hdparm?

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?

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.