marc@marc-laptop:~$ sudo /etc/init.d/hdapsd stop
[sudo] password for marc: 
marc@marc-laptop:~$ sudo hdapsd
Wed Dec 30 17:42:16 2009: Starting hdapsd
Wed Dec 30 17:42:16 2009: WARNING: You did not supply any devices to protect, trying autodetection.
Wed Dec 30 17:42:16 2009: Could not read from /sys/block/sda/device/unload_heads: Operation not supported
Wed Dec 30 17:42:16 2009: Could not detect any devices.
Usage: hdapsd [OPTIONS]

   -d --device=<device>              <device> is likely to be hda or sda.
                                     Can be given multiple times
                                     to protect multiple devices.
   -f --force                        Force unloading heads, even if kernel thinks
                                     differently (on pre ATA7 drives).
                                     This only works when adding devices by hand (-d).
   -s --sensitivity=<sensitivity>    How sensitive hdapsd should be to movements.
                                     Defaults to 15, higher value means less
                                     sensitive.
   -a --adaptive                     Adaptive threshold (automatic increase
                                     when the built-in keyboard/mouse are used).
   -v --verbose                      Get verbose statistics.
   -b --background                   Run the process in the background.
   -p --pidfile[=<pidfile>]          Create a pid file when running
                                     in background.
                                     If <pidfile> is not specified,
                                     it's set to /var/run/hdapsd.pid.
   -t --dry-run                      Don't actually park the drive.
   -y --poll-sysfs                   Force use of sysfs interface to
                                     accelerometer.
   -l --syslog                       Log to syslog instead of stdout/stderr.

   -V --version                      Display version information and exit.
   -h --help                         Display this message and exit.

You can send SIGUSR1 to deactivate hdapsd for 8 seconds.

Send bugs, comments and suggestions to hdaps-devel@lists.sourceforge.net