[CentOS] Running a command at startup

Thu Dec 13 00:04:12 UTC 2018
Robert Moskowitz <rgm at htt-consult.com>

On a support forum, I was told that to turn off my board's blue led run:

echo none | sudo tee /sys/class/leds/blue\:heartbeat/trigger

Well, this does not survive a system reboot.  So I was told:

Add the off bit to


Add it above "exit 0"

So of course, CentOS is past using rc.local and recommends:

# It is highly advisable to create own systemd services or udev rules
# to run scripts during boot instead of using this fi

So can someone point me to how to make this into a simple systemd service?