What is the preferred way to wipe external hard drives from Qubes? I wanted to use Dban to do so, but I am not sure I can “boot” it from ISO without leaving Qubes? Would be cool to run it in an AppVM to wipe an external USB hard drive.
dd, shred, wipe, …
see Securely wipe disk from ArchLinux wiki.
Yes, you can totally do this under Qubes as long as you attach that USB to the qube which will do the job. There is nothing inherently qubes-specific about this. It’s basically the same as doing the job on whatever operating system (apart from the USB attaching thing)