http://man.linuxde.net/systemctl

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

systemctl命令是系统服务管理器指令，它实际上将 service 和 chkconfig 这两个命令组合到一起。

| 任务 | 旧指令 | 新指令 |
| 使某服务自动启动 | chkconfig --level 3 httpd on | systemctl enable httpd.service |
| 使某服务不自动启动 | chkconfig --level 3 httpd off | systemctl disable httpd.service |
| 检查服务状态 | service httpd status | systemctl status httpd.service （服务详细信息） systemctl is-active httpd.service （仅显示是否 Active) |
| 显示所有已启动的服务 | chkconfig --list | systemctl list-units --type=service |
| 启动某服务 | service httpd start | systemctl start httpd.service |
| 停止某服务 | service httpd stop | systemctl stop httpd.service |
| 重启某服务 | service httpd restart | systemctl restart httpd.service |