Here are some tips and tricks about running Debian on the QNAP TS-209.
Automatic fan control
Debian ships a program called
qcontrol which can be used to control the
fan, LEDs and buttons on QNAP devices. You can edit the
/etc/qcontrol.conf configuration file to change the behaviour of
qcontrol, for example how the fans are regulated depending on the
temperature or which commands to run when a button is pressed.
Automatic power on
QNAP machines can turn on automatically when power is applied if the device was not powered down correctly. This is helpful when your power goes down. In order to enable this feature, run the following command:
sudo qcontrol --direct autopower on
Battery for clock
There's a CR-2032 battery hidden on the bottom of the main board (similar to the CMOS battery on most PCs). It's likely that the battery is dead after all these years and has to be replaced.