重启缓慢

这是不常发生的问题，今日遇到，特别记录下来。

1. 在幽兰中的控制台发出sudo reboot进行重启。
2. 幽兰的桌面消失，转为黑白两色的控制台，上面写着正在reboot字样。通常这里之后短暂停留，就开始新的启动界面了。但是今天停留了数十秒。
3. 连上幽兰的串口套件，收到很多调试信息：
   c
   Unattended-upgrade in progress during shutdown, please don’t turn off the computer
   [ * ] Job unattended-upgrades.service/stop running (4min 38s / 30min)
   Unattended-upgrade in progress during shutdown, please don’t turn off the computer
   [ *] Job unattended-upgrades.service/stop running (4min 41s / 30min)
   Unattended-upgrade in progress during shutdown, please don’t turn off the computer
   [** ] Job unattended-upgrades.service/stop running (4min 44s / 30min)
   Unattended-upgrade in progress during shutdown, please don’t turn off the computer
   [ ] Job unattended-upgrades.service/stop running (4min 47s / 30min)
   Unattended-upgrade in progress during shutdown, please don’t turn off the computer
   [* ] Job unattended-upgrades.service/stop running (4min 50s / 30min)
   Unattended-upgrade in progress during shutdown, please don’t turn off the computer
   [ *] Job unattended-upgrades.service/stop running (4min 53s / 30min)
   Unattended-upgrade in progress during shutdown, please don’t turn off the computer
   [ * ] Job unattended-upgrades.service/stop running (4min 56s / 30min)
   Unattended-upgrade in progress during shutdown, please don’t turn off the computer
   [ *** ] Job unattended-upgrades.service/stop running (4min 59s / 30min)
   Unattended-upgrade in progress during shutdown, please don’t turn off the computer

看起来是Ubuntu的后台自动升级服务阻碍了重启流程，在收到重启通知后，迟迟没有退出。
明确知道原因后，我一边写这篇短文，一边等了一会，系统便继续重启了。看来没有卡死，只是被耽搁了一阵子。