systemd systemctl 优秀文章

Systemd 入门教程：命令篇
http://www.ruanyifeng.com/blog/2016/03/systemd-tutorial-commands.html

http://www.jinbuguo.com/systemd/systemd-system.conf.html

linux下信号量介绍
https://www.cnblogs.com/frisk/p/11602973.html