解决buntu关机时间过长

按键盘 Esc 键可以发现，原来是 systemd 在等待90秒。屏幕显示: A stop job is running for Session

1.安装 watchdog
sudo apt install watchdog
2.开启 watchdog 服务
sudo systemctl enable watchdog.service
3.马上启用 watchdog 服务
sudo systemctl start watchdog.service