LinuxFocus.org: A serial line computer shutdown button and LED

“We will build a small device with 2 LEDs and one pushbutton. A
green LED will indicate when the pushbutton is active and a slowly
blinking yellow LED indicates that the server is working or still
in the process of shutting down. To shut down the server you press
the pushbutton for 3 seconds.”

“When you press the pushbutton then the green LED will go off
indicating the shutdown is in progress. The command “/sbin/shutdown
-t2 -h now” is now executing. The yellow LED continues blinking
while the server is still shutting down. When the yellow LED stops
blinking then you should still wait 10 seconds before you power off
the computer. The yellow LED stops when all processes are killed
and the disks are being unmounted. If your computer supports
automatic power off then you do not have to worry about the 10
seconds. Just wait until it has switched off it self.”

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