1. Edit your system's startup file Open up a terminal window, if your are using Linux Mint copy/paste the following: sudo pluma /etc/rc.local on Ubuntu use sudo gedit /etc/rc.local The difference is just in the standard graphical text editor application installed. You can of course install pluma on Ubuntu or gedit on Linux Mint if you like. 2. Composing the right command In a terminal window type hdparm -B /dev/sd? The drives that are set to a value higher than 127 (except 255) won't spin down, the drives that show "not supported" either manage this value on their own or are that old that they are not supporting power management at all. Talking about sata disks, the former is the most possible reason. To set the drive to the highest power saving level with the highest performance and yet allow it to spin down after 15 minutes type the following command in your rc.local file. Product and Serial being the output from sudo lshw -class disk hdparm -B...