hdparm.conf can be used to store hdparm settings permanently, ensuring they are automatically applied at every boot. However, for testing purposes, rebooting a machine multiple times can be inconvenient. Fortunately, with a simple command, changes made to the file can be applied live without the need for a system reboot.

The configuration file is mainly used by udev and with that said one can re-apply settings from in multiple ways. To apply the entire file you may run:

/usr/lib/pm-utils/power.d/95hdparm-apm resume

To apply changes relative to a single disk:

udevadm trigger /dev/disk/by-uuid/xxxxxx

That’s it!