pm2

                                    $ pm2 restart app_name
$ pm2 reload app_name
$ pm2 stop app_name
$ pm2 delete app_name

                                    # Monitoring CPU/Memory
pm2 monit
pm2 monitor
Make pm2 auto-boot at server restart:
pm2 startup
# Go To Server Directory Where you have store Express Files 
pm2 start app.js -o "/dev/null" -e "/dev/null"
# Freeze your process list across server restart
3.pm2 save
# Auto restart apps on file change
4. pm2 start app.js --watch
# Remove init script via:
$ pm2 unstartup systemd

                                    module.exports = {
  apps : [{
    name: "app",
    script: "./app.js",
    env: {
      NODE_ENV: "development",
    },
    env_production: {
      NODE_ENV: "production",
    }
  }, {
     name: 'worker',
     script: 'worker.js'
  }]
}

                                    $ npm install pm2@latest -g
# or
$ yarn global add pm2

                                    $ pm2 [list|ls|status]