# hd-idle > Spin down external disks after a period of idle time. > More information: . - Start a service to manage hard drive spin down. By default hard disks will spin down after 10 minutes of inactivity: `systemctl start hd-idle` - Spin down a disk immediately: `hd-idle -t {{/dev/sdX}}` - Set disks to never spin down, then set explicit idle times (in seconds) for disks which have "sda" or "sdb" in their device name: `hd-idle -i 0 -a /dev/sda -i {{300}} -a /dev/sdb -i {{1200}}`