This program monitors a GPIO pin on the Raspberry pi, and when that pin is activatedf for a specified, duration it runs a command
The initial purpose of the program was to monitor a shutdown button.
It also pulses an LED on a different GPIO in order to have a visible activity LED.
Useage is like:
powerman -led 16 -button 26 -debounce 2s -- sudo shutdown -h now
The above will set up a flashing LED on port 16, listen for a button on port 26, and if the button is depressed for 2 seconds, will run the command sudo shutdown -h now.
When running the specified command the LED changes flashing style from a slow flash to a rapid flash.
I have this set up as a systemd service in my Raspberry pi with the following unit (powerman.service):
[Unit]
Description=Power Button Monitoring Service
Documentation=https://github.com/rolfl/powerman
[Service]
ExecStart=/usr/local/bin/powerman -led 16 -button 26 -debounce 2s -- sudo shutdown -h now
ExecStop=/bin/echo Kill powerman manually with kill $MAINPID
KillMode=none
[Install]
WantedBy=multi-user.target
Note that it is intentional to ignore the systemd kill so that the fast-flashing LED lasts until the actual poweroff event.
You reconfigure systemd to accept the service with:
systemctl daemon-reload
systemctl enable powerman
systemctl start powerman
systemctl status powerman
Now, with the above service, when the system starts up and boots, the LED will start flashing, indicating that things are normal. Pressing the button for 2 seconds will trigger a "clean" system shutdown with a fast-flashing LED, until shutdown state is reached, at which point the LED turns off completely (indicating it is safe to unplug the system)