Depending on your laptop model, there are a few LEDs that can be controlled, at least under Linux. IBM and ASUS seem to use stuff in /proc/acpi/asus|ibm ... T

Depending on your laptop model, there are a few LEDs that can be controlled, at least under Linux. IBM and ASUS seem to use stuff in /proc/acpi/asus|ibm ... The SD-Card interface in my Laptop exports a LED in /sys/class/led... (but it seems not to be connected to anything). So there is often one or the other thing installed, but how to control them differs.