当我升级到 Ubuntu 18.04 并重新启动时，出现了“无法启动会话”错误。按下ctrl+alt+f1后，我进入了终端，然后使用sudo apt-get install --reinstall ubuntu-desktop，然后重新启动。
输入加密密码后，我看到此错误：
WARNING: Failed to connect to lvmetad. Falling back to device scanning.
Volume group "ubuntu-vg" not found
Cannot process volume group ubuntu-vg
WARNING: Failed to connect to lvmetad. Falling back to device scanning.
Reading all physical volumes. This may take a while...
Found volume group "ubuntu-vg" using metadata type lvm2
WARNING: Failed to connect to lvmetad. Falling back to device scanning.
2 logical volume(s) in volume group "ubuntu-vg" now active
/dev/mapper/ubuntu--vg-root: recovering journal
/dev/mapper/ubuntu--vg-root: clean, 487053/30203904 files, 66914067/120783872 blocks
WARNING: Failed to connect to lvmetad. Falling back to device scanning.
Volume group "ubuntu-vg" not found
Cannot process volume group ubuntu-vg
WARNING: Failed to connect to lvmetad. Falling back to device scanning.
Reading all physical volumes. THis may take a while...
Found volume group "ubuntu-vg" using metadata type lvm2
WARNING: Failed to connect to lvmetad. Falling back to device scanning.
2 logical volume(s) in volume group "ubuntu-vg" now active
/dev/mapper/ubuntu--vg-root: recovering journal
/dev/mapper/ubuntu--vg-root: clean, 487053/30203904 files, 66914067/120783872 blocks
此消息显示 1-4 秒，之后变黑，然后再次显示相同的消息。当我按任何键时都没有反应，除非我按alt+ f3（或类似键）登录终端可以短暂显示，然后完全变黑并继续循环。
我是 Ubuntu 新手。我该如何解决这个问题？