System LEDs

Each board led has a directory in /sys/class/leds. By default the LEDs use the following triggers:

LED Trigger
wifi_active phy0tx (WiFi Tx)
bt_active hci0tx (Bluetooth Tx)
user_led1 heartbeat
user_led2 mmc0 (disk access, eMMC)
user_led3 mmc1 (disk access, microSD card)
user_led4 CPU core 0 active(not used)

To change a user LED you can do the following as a root user:

# echo heartbeat > /sys/class/leds/<led_dir>/trigger      make a LED flash
# cat /sys/class/leds/<led_dir>/trigger                   show triggers
# echo none > /sys/class/leds/<led_dir>/trigger           remove triggers    
# echo 1 > /sys/class/leds/<led_dir>/brightness           turn LED on
# echo 0 > /sys/class/leds/<led_dir>/brightness           turn LED off