## 确保开启Crontab service，后台常驻


For ubuntu

```
$ sudo /etc/init.d/cron start 
```

## 编辑nCrontab

```
$ sudo crontab -e
```

[Linux Start Restart and Stop The Cron or Crond Service](https://www.cyberciti.biz/faq/howto-linux-unix-start-restart-cron/)

[在线Crontab表达式工具](http://www.atool.org/crontab.php)

[crontab执行不生效-【问题篇】](http://www.cnblogs.com/cuisi/p/6251848.html)