我将 ubuntu 版本从 ubuntu 16.04 升级到了 ubuntu 18.04 focal。重启后，系统要求我安装升级。但当我这样做时
sudo apt-get update
sudo apt-get upgrade
秒命令退出并显示错误，提示我需要安装 lxd。但安装 LXD 不起作用，自显示以下消息以来已有一个小时了。问题是什么？如何解决？
root@apulis-dev-infra02:~# apt-get install lxd
The following packages will be upgraded:
lxd
1 upgraded, 0 newly installed, 0 to remove and 1089 not upgraded.
2 not fully installed or removed.
Need to get 0 B/9,108 B of archives.
After this operation, 20.5 MB disk space will be freed.
Preconfiguring packages ...
(Reading database ... 250517 files and directories currently installed.)
Preparing to unpack .../archives/lxd_1%3a0.7_all.deb ...
=> Installing the LXD snap
==> Checking connectivity with the snap store
==> Installing the LXD snap from the 3.0 track for ubuntu-20.04
2020-01-09T17:24:52+08:00 INFO Waiting for restart...