升级后apt，我遇到了一些涉及 systemd 依赖循环的启动问题（例如zfs-linux#1875577）。因此，由于我在 ZFS 上运行 20.10（带加密），我决定使用 GRUB ZFS 历史条目恢复系统状态。然而，这显然让我遇到了这个错误使用rpool/ROOT/ubuntu_数据集（参见这个问题)，所以我仍然无法启动我的系统。此外，现在在启动过程中安装/var/lib/NetworkManager和/var/lib/apt失败。
我尝试通过从实时 USB 会话挂载 ZFS 文件系统来查看是否能够进行调查：
zpool export -a
zpool import -N -R /mnt rpool
zpool import -N -R /mnt bpool
cryptsetup open --type luks /dev/zvol/rpool/keystore keystore
mkdir -p /run/keystore/rpool
mount /dev/mapper/keystore /run/keystore/rpool
zfs load-key -a
zfs mount rpool/ROOT/ubuntu_<UUID>
zfs mount bpool/BOOT/ubuntu_<UUID>
zfs mount -a
结果zfs mount -a出现了与启动时类似的错误：
cannot mount '/mnt/var/lib/NetworkManager': failed to create mountpoint
cannot mount '/mnt/var/lib/apt': failed to create mountpoint
ls尝试看看发生了什么，我在/mnt/var/lib/NetworkManager和中看到了这些奇怪的问号/mnt/var/lib/apt，但这些路径也出现了访问错误。
$ ls -ahl /mnt/var/lib/
ls: cannot access '/mnt/var/lib/NetworkManager': No such file or directory
ls: cannot access '/mnt/var/lib/apt': No such file or directory
total 718K
drwxr-xr-x 80 root root 80 Nov 18 00:53 .
drwxr-xr-x 16 root root 18 Oct 22 14:17 ..
drwxr-xr-x 4 root root 4 Oct 22 14:01 AccountsService
drwxr-xr-x 2 root root 2 Jan 31 2019 acpi-support
drwxr-xr-x 2 root root 3 Dec 1 13:38 alsa
drwxr-xr-x 5 root root 5 Nov 18 00:54 apache2
drwxr-xr-x 4 root root 4 Dec 1 11:25 app-info
d????????? ? ? ? ? ? apt
drwxr-xr-x 2 root root 4 Nov 19 21:58 aptitude
drwxr-xr-x 2 root root 27 Oct 22 14:12 aspell
drwxr-xr-x 2 avahi-autoipd avahi-autoipd 2 Oct 22 14:09 avahi-autoipd
drwxr-xr-x 2 root root 5 Nov 15 23:06 binfmts
drwxr-xr-x 3 root root 3 Nov 15 13:40 bluetooth
drwxr-xr-x 2 root root 2 Jun 16 14:01 boltd
drwxrwxrwt 2 root root 2 Jul 27 15:38 BrlAPI
drwxr-xr-x 4 colord colord 6 Nov 15 15:01 colord
drwxr-xr-x 2 root root 4 Dec 1 11:25 command-not-found
drwxr-xr-x 2 root root 3 Nov 15 15:01 dbus
drwxr-xr-x 2 root root 2 Aug 12 09:33 dhcp
drwxr-xr-x 5 root root 5 Oct 22 14:08 dictionaries-common
drwxr-xr-x 3 root root 4 Dec 1 12:05 dkms
drwxr-xr-x 7 root root 18 Dec 1 12:06 dpkg
drwxr-xr-x 3 root root 3 Oct 22 14:02 emacsen-common
drwxr-xr-x 2 root root 2 Apr 16 2020 fprint
drwxr-xr-x 6 root root 7 Nov 15 23:05 fwupd
drwxr-xr-x 5 gdm gdm 6 Dec 1 13:30 gdm3
drwxr-xr-x 3 root root 3 Nov 15 22:59 gems
drwxr-xr-x 2 geoclue geoclue 2 Feb 28 2020 geoclue
drwxr-xr-x 4 root root 4 Oct 22 14:03 ghostscript
drwxr-xr-x 2 root root 2 Jun 9 20:50 git
drwxr-xr-x 4 root root 4 Oct 22 14:04 grub
drwxr-xr-x 2 root root 2 Jun 22 10:09 hp
drwxr-xr-x 2 root root 6 Nov 25 11:32 initramfs-tools
drwxr-xr-x 2 root root 3 Oct 22 14:02 ispell
drwxr-xr-x 3 root root 3 Oct 22 14:05 libreoffice
drwxr-xr-x 3 root root 3 Nov 15 22:59 libxml-sax-perl
drwxr-xr-x 3 root root 3 Oct 22 14:12 locales
drwxr-xr-x 2 root root 3 Nov 30 23:00 logrotate
drwxr-xr-x 2 root root 3 Oct 22 14:10 man-db
drwxr-xr-x 2 root root 2 Oct 16 15:40 misc
d????????? ? ? ? ? ? NetworkManager
drwxr-xr-x 3 root root 3 Oct 22 14:10 openvpn
drwxr-xr-x 2 root root 2 Dec 1 12:55 os-prober
drwxr-xr-x 2 root root 3 Dec 1 13:31 PackageKit
drwxr-xr-x 2 root root 8 Nov 19 21:57 pam
drwxr-xr-x 4 root root 4 Nov 15 23:35 php
drwxr-xr-x 2 root root 3 Nov 15 15:01 plymouth
drwx------ 3 root root 3 Oct 22 13:59 polkit-1
drwx------ 2 root root 2 Oct 22 13:59 private
drwxr-xr-x 2 root root 3 Oct 22 13:59 python
drwxr-xr-x 2 root root 2 Sep 8 18:15 realmd
drwxr-xr-x 2 root root 4 Nov 19 21:57 sgml-base
drwxr-xr-x 3 root root 5 Nov 15 15:18 shim-signed
drwxr-xr-x 24 root root 26 Dec 1 13:30 snapd
drwxr-xr-x 2 root root 2 Aug 6 15:42 snmp
drwxr-xr-x 10 root root 10 Oct 22 14:09 sss
drwxr-xr-x 3 root root 3 Oct 22 13:59 sudo
drwxr-xr-x 2 root root 2 Feb 28 2020 synaptic
drwxr-xr-x 12 root root 13 Nov 15 15:01 systemd
drwxr-xr-x 5 root root 5 Nov 15 22:59 tex-common
drwxr-xr-x 9 root root 16 Nov 18 00:54 texmf
drwx--S--- 3 127 135 9 Dec 1 13:38 tor
drwxr-xr-x 2 tss tss 2 Dec 3 2019 tpm
drwxr-xr-x 2 root root 3 Nov 15 13:46 ubiquity
drwxr-xr-x 2 root root 2 Sep 1 17:14 ubuntu-advantage
drwxr-xr-x 2 root root 3 Nov 15 15:01 ubuntu-drivers-common
drwxr-xr-x 2 root root 2 Nov 28 13:17 ubuntu-release-upgrader
drwxr-xr-x 3 root root 21 Nov 18 01:28 ucf
drwx------ 2 root root 3 Dec 1 13:30 udisks2
drwxr-xr-x 2 root root 2 Aug 5 12:03 unattended-upgrades
drwxr-xr-x 2 root root 2 Jul 23 19:50 update-manager
drwxr-xr-x 4 root root 6 Dec 1 12:06 update-notifier
drwxr-xr-x 2 root root 6 Dec 1 13:05 upower
drwxr-xr-x 2 root root 2 Jul 27 16:30 usb_modeswitch
drwxr-xr-x 2 root root 3 Oct 22 14:02 usbutils
drwxr-xr-x 3 root root 3 Oct 22 13:59 vim
drwxr-xr-x 2 root root 3 Dec 1 13:30 whoopsie
drwxr-xr-x 2 root root 3 Oct 22 14:10 xfonts
drwxr-xr-x 2 root root 3 Oct 22 14:04 xkb
drwxr-xr-x 2 root root 6 Oct 22 14:11 xml-core
尝试访问或删除这些路径会声称不存在这样的文件，而尝试访问或删除mkdir这些路径会声称这些文件已经存在！（这就是无法创建挂载点的原因。）
$ ls /mnt/var/lib/NetworkManager
ls: cannot access '/mnt/var/lib/NetworkManager': No such file or directory
$ rm /mnt/var/lib/NetworkManager
rm: cannot remove '/mnt/var/lib/NetworkManager': No such file or directory
$ rmdir /mnt/var/lib/NetworkManager
rmdir: failed to remove '/mnt/var/lib/NetworkManager': No such file or directory
$ mkdir /mnt/var/lib/NetworkManager
mkdir: cannot create directory ‘/mnt/var/lib/NetworkManager’: File exists
这里发生了什么？我该如何摆脱这些路径条目？