This simple script allows to disable all router LEDs (except power-on) at once, or enable them by resetting to default settings.
Can be useful for anyone who doesn't like LEDs blinking in the face at night.
Add something like this to crontab:
0 21 * * * /root/openwrt_leds_control.sh disable_all
0 6 * * * /root/openwrt_leds_control.sh reset