Stoppen the blinkenlights

In Linux, pretty much everything is a file: A file is a file, a directory is a file, and devices are files, too. These files are not always readable and writeable, but you can try to use some standard file operations on them. For the LEDs, writing 0 or 1 to certain files in /sys/class/leds/... makes the LEDs go on and off:

Assuming you have an ssh connection to your beaglebone, switch to a "root" session by typing:

sudo -s

You should now see something like "root\@bbb-bob" in the terminal. Be careful in root sessions - the root user has full adminstration rights, and Ubuntu won't ask you safety questions like "Are you sure you want to mess up your system?".

Switch off the first of the four system LEDS

Note: On some newer distributions, these LEDs were renamed slightly. Go into the folder "/sys/class/leds/" and poke around a bit. Mine is now called "/sys/class/leds/beaglebone:green:heartbeat".

By default, the first LED blinks in a heartbeat pattern, which can be quite annoying. Let's switch that off.

Go to the folder of the LED. On an older distribution, it is:

cd /sys/class/leds/beaglebone\:green\:usr0/

On a newer distribution, the path is

cd /sys/class/leds/beaglebone:green:heartbeat/

The blinking is triggered by whatever is set in the file "trigger". Let's have a look at that file. The command "cat" gives us the content of the file "trigger" on the standard output:

cat trigger

For me, the file looks something like

none rc-feedback mmc0 mmc1 timer oneshot [heartbeat] 
backlight gpio cpu0 default-on

The brackets [ ] indicate that it is currently set to "hearbeat". We'll disable the heartbeat pattern by setting the trigger to "none":

echo none > trigger

The command "echo none" means: Repeat the string "none" to the standard output. The ">" redirects the standard output to whatever stands on the right side of ">". You can think of the ">" command as an arrow that points the output of one command to the input of another. The "command" on the right is a file-name, so the "none" is simply written to that file.
The file is, of course, not an actual text file, but a special interface file that tells the BeagleBone to set the trigger of the LED off.

Now you can manually set the LED on and off:

Assuming you are on an older distribution, do:

echo 0 > brightness
echo 1 > brightness

Disable the "blinking" of the LEDs on boot

There are many different ways to do stuff every time the computer starts. I put the command that disables the blinking of the LEDs into the rc.local file by callling the command

sudo nano /etc/rc.local

and inserting the following lines between all the comments and the "exit 0" line:

# Disable the blinking of the LEDs, for older distributions
 echo none > /sys/class/leds/beaglebone\:green\:usr0/trigger
 echo none > /sys/class/leds/beaglebone\:green\:usr1/trigger
 echo none > /sys/class/leds/beaglebone\:green\:usr2/trigger
 echo none > /sys/class/leds/beaglebone\:green\:usr3/trigger

For newer distributions, the lines have to read

# Disable the blinking of the LEDs, for newer distributions
echo none > /sys/class/leds/beaglebone\:green\:heartbeat/trigger
echo none > /sys/class/leds/beaglebone\:green\:mmc0/trigger
echo none > /sys/class/leds/beaglebone\:green\:usr2/trigger
echo none > /sys/class/leds/beaglebone\:green\:usr3/trigger

Now, when I reboot my BeagleBone using

sudo reboot

the lights flash for 10 seconds while the BeagleBone finishes booting, but then go dark as soon as booting is finished.