This is begin with I try to eject the external hdd from my laptop. Then, I found out that the ext hdd still spinning. Usually I left it that way. I unplug the cable and I heard the ‘tring’ sound. I know that is not good. The hdd could be damage.
So tonight I wonder if there is a command to eject the hdd but also to spin off the hdd. And I found one. I forget the link sorry. Some wiki linux thing.
Here is the command :
#sudo udisksctl power-off -b /dev/sdx
I heard the hdd stop spinning. Then I unplugged it. It is safe.