Você pode usar hdparm -C /dev/sda
. De man hdparm
:
-C Check the current IDE power mode status, which will always be one
of unknown (drive does not support this command), active/idle
(normal operation), standby (low power mode, drive has spun down),
or sleeping (lowest power mode, drive is completely shut down).
The -S, -y, -Y, and -Z options can be used to manipulate the IDE
power modes.