Please update README with instructions to control njspc with systemd

[dkossman]

This systemd setup worked for me on Raspbian - can you add to the README? Seems like it might be helpful for others. This is based on a gitter post by @guru-florida, slightly adjusted for my configuration.

pi> sudu vi /etc/systemd/system/poolController.service # or your favorite editor

this file should contain the following. You may need to edit to adjust the user, working directory, or start command for your installation and OS:

[Unit]
Description=NodeJS Pool Controller
Documentation=https://github.com/tagyoureit/nodejs-poolController/
After=network.target

[Service]
Environment=NODE_ENV=production
Type=simple
User=pi
WorkingDirectory=/home/pi/nodejs-poolController
ExecStart=/usr/local/bin/node dist/app.js
Restart=on-failure
RestartSec=15s

[Install]
WantedBy=multi-user.target

Then run these commands:

pi> sudo systemctl daemon-reload
pi> sudo systemctl enable poolController
pi> sudo systemctl start poolController

To check the status of the service:
pi> systemctl status poolController

To tail the log:
pi> sudo -n journalctl -o cat -n 2500 -f -u poolController # tail the poolController log, -u option is based on service name

To stop, restart or disable the service, use the appropriate systemctl command:

pi> sudo systemctl stop poolController
pi> sudo systemctl restart poolController
pi> sudo systemctl disable poolController

[tagyoureit]

Added this to the wiki and added to Readme! Thanks very much.