Motherboard LED

Using Cloudmesh to Control the LEDs

The most convenient way to control the motherboard LEDs is via Cloudmesh. It includes a special command that can even be called from a remote Pi using ssh once you hve set up the cluster with cloudmesh.

This command switches on and off the LEDs of the specified PIs. If the hostname is omitted. It is assumed that the code is executed on a PI and its LED are set.

The specialty of this program is that it not only can query the current state, but also allows you to set multiple LEDs on different motherboards at the same time with a convenient parameterized syntax.

Examples

We present a number of examples on how to use this command

cms pi led list  "red,red[01-03]"

lists the LED status of the given hosts

cms pi led red off  "red,red[01-03]"

switches off the led of the given PIs

cms pi led red on  "red,red[01-03]"

switches on the led of the given PIs

cms pi led red blink  "red,red[01-03]"

switches on and off the led of the given PIs

cms pi led red sequence  "red,red[01-03]"

goes in sequential order and switches on and off the led of the given PIs

Syntax

The command syntax is

cms pi led reset [NAMES]
cms pi led (red|green) VALUE
cms pi led (red|green) VALUE NAMES [--user=USER]
cmspi led list NAMES [--user=USER]

Using Motherboard LEDs from Shell Scripts

The Raspberry pi contains an LED that can also be used to provide us with some information as to the status of the PI. It is usually used for reporting the power status.

The green LED can be made blinking as follows in root

echo 1 > /sys/class/leds/led0/brightness
echo 0 > /sys/class/leds/led0/brightness

Controlling the Motheboard LEDs remotely via ssh

Naturally this ac be done via a remote command if your ssh keys are uploaded and your originating computer is added to the authorized_keys. Now you can can control them via ssh

ssh pi@red03 "echo 1 > led; sudo cp led /sys/class/leds/led0/brightness"
ssh pi@red03 "echo 0 > led; sudo cp led /sys/class/leds/led0/brightness"

This is extremely useful as it allows us to check if we the OS is available and we can access the PI.

One strategy is to for example switch the light of, once it is booted, so we can see which board may be in trouble.