I'm running Debian (Raspbmc). I have a number of external hard drives connected via USB. These HDD are powered by an external power supply.
Since I often fall asleep while watching movies, I want to automatically shut down my machine after 2 hours. This is not a problem with the machine (Debian) itself , but my external HDD are still running and are extremely loud. Is there any way I can't stop these HDD from spinning via the OS? And is this safe (since there is still a running power source)?