You can control the front LEDs (as well as triggering other hardware events) on a Synology NAS by sending certain values to /dev/ttyS1, either from a script of from the CLI via Telnet or SSH.
These commands “force” the LED state, and therefore the LEDs can’t be used as status indicators after being forced. You can, however, simply reboot the NAS to restore normal operation; the settings do not survive a reboot.
Below are a list of commands that can be run from the command line (if you are logged in as root) or incorportated into a script. Note that the # character and everything after it are comments, and some characters require escaping.
These are only the commands I could get to work on my NAS.
echo 1>/dev/ttyS1 # Immediate power off (not graceful)
echo 4>/dev/ttyS1 # Power LED on solid
echo 5>/dev/ttyS1 # Power LED flash
echo 6>/dev/ttyS1 # Power LED off
echo 7>/dev/ttyS1 # Status LED off
echo 8>/dev/ttyS1 # Status LED on solid green
echo A>/dev/ttyS1 # USBCopy LED flash
echo @>/dev/ttyS1 # USBCopy LED on solid
echo B>/dev/ttyS1 # USBCopy LED off
echo C>/dev/ttyS1 # Immediate reset (not graceful)
echo :>/dev/ttyS1 # Status LED on solid amber
echo ;>/dev/ttyS1 # Status LED flashing amber
If you know if any other values to send to ttyS1, or anything else you’d like to share regarding this, please feel free to do so in the comments below. Thank you!