crontab

@reboot ~/node-app-starter.sh >> cron.log 2>&1

node-app-starter.sh

#!/bin/sh

if [ $(ps aux | grep $USER | grep node | grep app.js | grep -v grep | wc -l | tr -s "\n") -eq 0 ]
then
        export NODE_ENV=production
        export PATH=/usr/local/bin:$PATH
        forever start ~/example/app.js > /dev/null
fi