Since the GuruPlug doesn't have a screen, it's hard to know if the system has booted properly. Fortunately, the GuruPlug has LEDs on it, and we can use those LEDs to check that the system is booting properly. The Linux kernel has direct device support for the LEDs, and they can be set to flash at various rates; indicate disk, flash memory, or wireless activity; or show a heartbeat pattern (double flash, indicating that the system is running). Let's program them the red LEDs to flash show a heartbeat when the system is booted.