You can get a list of all controllable LEDs by checking the content of the virtual directory
$ ls /sys/class/leds/
input5::capslock input5::numlock input5::scrolllock
On my system, there are only the three keyboard LEDs. If your output looks different, make sure you use the correct names instead below!
Each file is a symbolic link to a directory holding several properties of that LED:
$ ls '/sys/class/leds/input5::capslock'
brightness device max_brightness power subsystem trigger uevent
The only thing which is important for us is the
brightness file content.
0 means the LED is off.
1 means the LED is on. (Assuming the
max_brightness file holds the value 1 - on special keyboards the LED might maybe support multiple brightness values?)
We get the current LED state by checking the
brightness file's content (it's currently off):
$ cat '/sys/class/leds/input5::capslock/brightness'
To switch the LED on, we must set that file's content to
$ echo 1 | sudo tee '/sys/class/leds/input5::capslock/brightness'
To switch the LED on during every boot, you might want to append the command below to your
/etc/rc.local script. It will be executed as root, therefore we don't need the
sudo tee but can use Bash output redirection:
$ echo 1 > '/sys/class/leds/input5::capslock/brightness'