I am running the latest Ubuntu (2015-02-19) from Robert Nelson. I have a Seagate Expansion 4TB external HDD connected through an unpowered USB hub. Everything seems to work fine, except for the fact that the HDD never sleeps. This is for a backup, so I just want it to run when the backup process is running. Instead, it runs all the time.
Any idea how to get it to properly sleep?