切换到第三运行级
systemctl isolate multi-user.target 或 systemctl isolate runlevel3.target
切换到第五运行级别
systemctl isolate graphical.target 或 systemctl isolate runlevel5.target
设置默认第三启动级别
systemctl set-default multi-user.target
设置默认第五启动级别
systemctl set-default graphical.target
查看当前默认的启动级别
systemctl get-default
