[Unit]
Description=Control Raspberry Pi PWR (power) LED

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=sh -c "echo 1 > /sys/class/leds/PWR/brightness"
ExecStop=sh -c "echo 0 > /sys/class/leds/PWR/brightness"

[Install]
WantedBy=multi-user.target

# systemctl daemon-reload
# systemctl enable rpi-led-pwr.service
# systemctl start rpi-led-pwr.service