Update-smart-drivedb... probably no longer compatible

root@osmc:/home/osmc# /usr/sbin/update-smart-drivedb
/var/lib/smartmontools/drivedb/drivedb.h.error: rejected by /usr/sbin/smartctl, probably no longer compatible

What smartctl database we are using?

OSMC doesn’t ship with smart tools installed. If you have installed them they will be either Raspbian (Pi 1) or Debian Jessie (Pi 2/3) versions of the packages.

If you don’t use smartctl, then what mechanism do you use for spinning down hard drives?

I thought that my WD Green 4 TB is not in the smartctl database, now I am not sure what to do in order to enable spinning down.

I find it strange that you asked this question when @DBMandrake already 4 months ago told you exactly how it is being done in OSMC with hdparm.

WD Green drives are quite special in their power management and you might google a bit around that topic.