指令格式
systemctl [command] [unit]
常用指令
1.启动
$ systemctl start
2.停止
$ systemctl stop
3.重启
$ systemctl restart
4.不关闭unit的情况下，重新加载配置文件
$ systemctl reload
5.开机自启
$ systemctl enable
6.开机不自启
$ systemctl disable
7.查看unit的状态
$ systemctl status
8.查看unit是否正在运行
$ systemctl is-active
9.开机时是否自启此unit
$ systemctl is-enable
10.列出unit的配置
$ systemctl show
11.注销此unit，之后就无法启动此unit了
$ systemctl mask
12.反注销
$ systemctl unmask
13.查看已启动的服务
$ systemctl list -units --type=service