I actually can't really program but I did my first copy and paste program cause I wanted to annoy a friend by opening and closing his cd drive non stop... Well most people don't know what cd drives are these days anyways... Imagine it like your pc constantly unmounting the USB thumbdrive or external HDD.

I have a 128GB USB 3 flash drive. I have it formatted as NTFS as that is the only filesystem that seems to work on both Ubuntu 18.04 and Windows 10. All the others I tried would have errors and/or corrupt data.

The problem is when I copy say 5GB of data to the drive on Ubuntu, it shows a file copying dialog, and then completes. Then I go to unmount the drive and it takes about 5 minutes to finish unmounting. It always brings up a dialog on the desktop saying do not remove the drive.

What is going on that it takes that long to unmount?

Just wanted to make a clean install on my iMac. What could possibly go wrong?!

Cleaning the hard disk was interrupted by a process running (kextcache). Catalina wouldn't install ("Incomplete systen on target device". Dropping the terminal I could somehow force unmounting and wipe the disk. Had a BSOD in between. Catalina would still not install ("Failed to install pre boot volume"). Later erasing the disk got blocked by the kernel itself. Felt like trouble and it was: Next time I was greeted with a blinking folder containing a questionmark instead of the bitten Apple.

Last resort: Internet recovery. Installing El Capitan was said to take 7 hours so I took a USB time machine backup of latest Catalina. Installed it, but on reboot it get's stuck when progress bar is at 100%. But at least I've a working recovery again. Yeah, progress!