我的系统启动正常，但我试图解决几个与 ZFS 相关的启动错误，如下所示：
cannot mount '/root': directory is not empty
cannot mount '/var/cache': directory is not empty
凭借我的无限智慧，我将“rpool/var/cache /var/cache zfs defaults 0 0”添加到我的 fstab 中，我的系统无法重新启动，它将我踢到终端，在那里我可以从 fstab 中删除该行并重新启动我的系统。以下是 /etc/fstab 的当前状态：
rpool/var/log /var/log zfs defaults 0 0
rpool/var/tmp /var/tmp zfs defaults 0 0
/dev/zvol/rpool/swap none swap defaults 0 0
有一件奇怪的事情，在它重新启动后，它陷入了登录循环，我不得不进入终端，username按照主目录中的这些说明。
现在 rpool 无法挂载，结果我的主目录中的文件夹以及所有文件都丢失了，因为我的许多系统文件夹都是从 rpool 继承的。我的 ZFS 如下所示：
$ zfs get mountpoint,mounted,canmount,overlay rpool -t filesystem -r
NAME PROPERTY VALUE SOURCE
rpool mountpoint / local
rpool mounted no -
rpool canmount on local
rpool overlay off default
rpool/ROOT mountpoint none local
rpool/ROOT mounted no -
rpool/ROOT canmount off local
rpool/ROOT overlay off local
rpool/ROOT/ubuntu mountpoint / local
rpool/ROOT/ubuntu mounted yes -
rpool/ROOT/ubuntu canmount noauto local
rpool/ROOT/ubuntu overlay off inherited from rpool/ROOT
rpool/home mountpoint /home inherited from rpool
rpool/home mounted no -
rpool/home canmount on default
rpool/home overlay off default
rpool/home/greg mountpoint /home/greg inherited from rpool
rpool/home/greg mounted yes -
rpool/home/greg canmount on default
rpool/home/greg overlay off default
rpool/home/root mountpoint /root local
rpool/home/root mounted no -
rpool/home/root canmount on default
rpool/home/root overlay off default
rpool/srv mountpoint /srv inherited from rpool
rpool/srv mounted yes -
rpool/srv canmount on default
rpool/srv overlay off default
rpool/var mountpoint /var inherited from rpool
rpool/var mounted no -
rpool/var canmount off local
rpool/var overlay off default
rpool/var/cache mountpoint /var/cache inherited from rpool
rpool/var/cache mounted yes -
rpool/var/cache canmount on default
rpool/var/cache overlay off default
rpool/var/games mountpoint /var/games inherited from rpool
rpool/var/games mounted yes -
rpool/var/games canmount on default
rpool/var/games overlay off default
rpool/var/log mountpoint legacy local
rpool/var/log mounted yes -
rpool/var/log canmount on default
rpool/var/log overlay off default
rpool/var/mail mountpoint /var/mail inherited from rpool
rpool/var/mail mounted yes -
rpool/var/mail canmount on default
rpool/var/mail overlay off default
rpool/var/spool mountpoint /var/spool inherited from rpool
rpool/var/spool mounted yes -
rpool/var/spool canmount on default
rpool/var/spool overlay off default
rpool/var/tmp mountpoint legacy local
rpool/var/tmp mounted yes -
rpool/var/tmp canmount on default
rpool/var/tmp overlay off default
我的所有池都在我的 zpool 列表中：
$ zpool list
NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
Pool-1tb 976G 414G 562G - 4% 42% 1.00x ONLINE -
Pool-500gb 488G 70.1G 418G - 0% 14% 1.00x ONLINE -
rpool 952G 684G 268G - 57% 71% 1.00x ONLINE -
启动后我无法挂载 rpool：
$ zfs mount rpool
cannot mount '/': directory is not empty
这是我运行 journalctl -b 时出现的当前 ZFS 相关错误：
关于如何在启动时挂载 rpool 以及如何恢复系统，有什么建议吗？
使用 zfsutils-linux 0.7.5 和 zfs-dkms 0.7.5 运行 Ubuntu 18.04
编辑：
df -h on / 的输出
$ ls -la
total 174
drwxr-xr-x 26 root root 30 Apr 29 06:58 .
drwxr-xr-x 26 root root 30 Apr 29 06:58 ..
drwxr-xr-x 2 root root 166 Apr 29 06:56 bin
drwxr-xr-x 4 root root 22 May 5 06:21 boot
drwxr-xr-x 24 root root 5380 May 5 07:22 dev
drwxr-xr-x 154 root root 265 May 5 07:24 etc
drwxr-xr-x 3 root root 3 May 4 12:21 home
lrwxrwxrwx 1 root root 33 Apr 29 06:58 initrd.img -> boot/initrd.img-4.15.0-99-generic
lrwxrwxrwx 1 root root 33 Apr 29 06:58 initrd.img.old -> boot/initrd.img-4.15.0-96-generic
drwxr-xr-x 24 root root 37 Apr 20 18:58 lib
drwxr-xr-x 2 root root 45 Jan 20 2019 lib32
drwxr-xr-x 2 root root 3 Jul 10 2019 lib64
drwxr-xr-x 3 root root 3 May 3 01:32 media
drwxr-xr-x 2 root root 2 Apr 27 2018 mnt
drwxr-xr-x 13 root root 13 Mar 29 12:34 opt
drwxr-xr-x 5 greg root 5 Apr 23 11:42 Pool-1tb
drwxr-xr-x 6 greg root 6 Apr 21 14:17 Pool-500gb
dr-xr-xr-x 1325 root root 0 May 5 07:21 proc
drwxr-xr-x 11 root root 12 Apr 20 19:27 root
drwxr-xr-x 37 root root 1140 May 5 07:22 run
drwxr-xr-x 2 root root 218 May 2 17:25 sbin
drwxr-xr-x 16 root root 17 Apr 30 13:02 snap
drwxr-xr-x 2 root root 2 Apr 27 2018 srv
dr-xr-xr-x 13 root root 0 May 5 07:21 sys
drwxrwxrwt 20 root root 21 May 5 07:31 tmp
drwx------ 4 root root 4 Apr 28 2018 .Trash-0
drwxr-xr-x 12 root root 12 Jul 27 2019 usr
drwxr-xr-x 15 root root 17 Apr 27 2018 var
lrwxrwxrwx 1 root root 30 Apr 29 06:58 vmlinuz -> boot/vmlinuz-4.15.0-99-generic
lrwxrwxrwx 1 root root 30 Apr 29 06:58 vmlinuz.old -> boot/vmlinuz-4.15.0-96-generic
/home 上的 ls -la 的输出
$ ls -la
total 18
drwxr-xr-x 3 root root 3 May 4 12:21 .
drwxr-xr-x 26 root root 30 Apr 29 06:58 ..
drwxr-xr-x 22 greg greg 25 May 5 08:46 greg
/home/greg 上的 ls -la 的输出
$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 95G 0 95G 0% /dev
tmpfs 19G 4.6M 19G 1% /run
rpool/ROOT/ubuntu 258G 24G 235G 10% /
tmpfs 95G 4.0K 95G 1% /dev/shm
tmpfs 5.0M 4.0K 5.0M 1% /run/lock
tmpfs 95G 0 95G 0% /sys/fs/cgroup
rpool/var/log 236G 1.4G 235G 1% /var/log
rpool/var/tmp 235G 128K 235G 1% /var/tmp
/dev/loop0 161M 161M 0 100% /snap/gnome-3-28-1804/116
/dev/loop3 94M 94M 0 100% /snap/core/9066
/dev/loop1 94M 94M 0 100% /snap/darktable-kyrofa/49
/dev/loop4 243M 243M 0 100% /snap/gnome-3-34-1804/27
/dev/loop2 141M 141M 0 100% /snap/gnome-3-26-1604/97
/dev/loop5 116M 116M 0 100% /snap/checksum-validator/2
/dev/loop6 141M 141M 0 100% /snap/gnome-3-26-1604/98
/dev/loop7 157M 157M 0 100% /snap/gnome-3-28-1804/110
/dev/loop8 2.5M 2.5M 0 100% /snap/gnome-calculator/730
/dev/loop9 93M 93M 0 100% /snap/darktable-kyrofa/45
/dev/loop10 44M 44M 0 100% /snap/snap-store/415
/dev/loop11 94M 94M 0 100% /snap/core/8935
/dev/loop12 63M 63M 0 100% /snap/gtk-common-themes/1506
/dev/loop13 143M 143M 0 100% /snap/slack/23
/dev/loop14 143M 143M 0 100% /snap/slack/22
/dev/loop15 55M 55M 0 100% /snap/core18/1705
/dev/loop16 62M 62M 0 100% /snap/authy/3
/dev/loop17 55M 55M 0 100% /snap/gtk-common-themes/1502
/dev/loop18 9.2M 9.2M 0 100% /snap/canonical-livepatch/95
/dev/loop19 55M 55M 0 100% /snap/core18/1754
/dev/loop20 4.4M 4.4M 0 100% /snap/gnome-calculator/704
Pool-1tb 946G 415G 532G 44% /Pool-1tb
Pool-500gb 473G 71G 403G 15% /Pool-500gb
rpool/srv 235G 128K 235G 1% /srv
rpool/var/games 235G 128K 235G 1% /var/games
rpool/var/mail 235G 128K 235G 1% /var/mail
tmpfs 19G 16K 19G 1% /run/user/120
tmpfs 19G 36K 19G 1% /run/user/1000
ls -la on / 的输出
$ ls -la
ls: cannot access '.gvfs': Permission denied
total 69
drwxr-xr-x 23 greg greg 26 May 5 07:22 .
drwxr-xr-x 3 root root 3 May 4 12:21 ..
-rw------- 1 greg greg 2938 May 5 07:24 .bash_history
drwx------ 18 greg greg 20 May 5 05:57 .cache
drwx------ 17 greg greg 20 May 4 17:49 .config
drwx------ 3 root root 3 May 4 13:07 .dbus
drwxr-xr-x 2 greg greg 2 May 4 13:04 Desktop
drwxr-xr-x 2 greg greg 2 May 4 13:04 Documents
drwxr-xr-x 2 greg greg 2 May 4 13:04 Downloads
drwx------ 2 greg greg 2 May 4 13:04 .gconf
drwx------ 3 greg greg 5 May 4 13:06 .gnupg
d????????? ? ? ? ? ? .gvfs
-rw------- 1 greg greg 2480 May 5 07:22 .ICEauthority
drwx------ 3 greg greg 3 May 4 13:04 .local
drwx------ 5 greg greg 5 May 4 17:49 .mozilla
drwxr-xr-x 2 greg greg 2 May 4 13:04 Music
drwxr-xr-x 2 greg greg 2 May 4 12:21 NAS
drwx------ 3 greg greg 3 May 4 13:04 .nv
drwxr-xr-x 2 greg greg 3 May 5 05:57 Pictures
drwx------ 3 greg greg 3 May 4 17:49 .pki
drwxr-xr-x 2 greg greg 2 May 4 13:04 Public
drwxr-xr-x 3 greg greg 3 May 4 13:06 snap
drwx------ 2 greg greg 2 May 4 13:06 .ssh
-rw-r--r-- 1 greg greg 0 May 4 13:07 .sudo_as_admin_successful
drwxr-xr-x 2 greg greg 2 May 4 13:04 Templates
drwxr-xr-x 2 greg greg 2 May 4 13:04 Videos
/root 上的 ls -la 的输出
$ ls -la
total 42
drwxr-xr-x 11 root root 12 Apr 20 19:27 .
drwxr-xr-x 26 root root 30 Apr 29 06:58 ..
-rw------- 1 root root 399 May 4 12:59 .bash_history
drwx------ 4 root root 4 Apr 28 2018 .cache
drwx------ 6 root root 6 Jun 23 2018 .config
drwx------ 3 root root 3 Apr 28 2018 .dbus
drwx------ 2 root root 3 Apr 20 20:01 .ecryptfs
drwx------ 2 root root 2 Nov 8 2018 .gconf
drwxr-xr-x 2 root root 3 May 5 07:21 .hplip
drwxr-xr-x 3 root root 3 Apr 28 2018 .local
drwxr-xr-x 3 root root 3 Mar 29 19:01 snap
drwx------ 3 root root 6 May 5 06:24 .synaptic
/var/cache 上的 ls -la 的输出
$ ls -la
total 142
drwxr-xr-x 18 root root 19 Feb 18 06:30 .
drwxr-xr-x 15 root root 17 Apr 27 2018 ..
drwx------ 2 root root 22 Apr 30 13:02 apparmor
drwxr-xr-x 4 root root 4 Dec 6 2018 app-info
drwxr-xr-x 3 root root 5 May 5 06:21 apt
drwxr-xr-x 2 root root 6 Apr 29 2018 cracklib
drwxrwx--- 3 root lp 11 May 5 06:31 cups
drwxr-xr-x 2 root root 7 May 5 06:21 debconf
drwxr-xr-x 2 root root 153 Apr 30 13:02 fontconfig
drwxr-xr-x 2 root root 4 May 4 13:05 fwupd
drwxr-xr-x 2 root root 2 Jun 5 2018 gdm
drwx------ 2 root root 3 May 2 17:26 ldconfig
drwxr-xr-x 35 man man 37 May 5 06:21 man
-rw-r--r-- 1 root root 227 May 5 05:28 motd-news
drwxr-xr-x 3 root root 3 Sep 3 2018 PackageKit
drwxr-xr-x 3 root root 5 May 5 07:22 samba
drwx------ 2 root root 2 Aug 30 2016 slack
drwxr-xr-x 3 root root 6 May 4 15:28 snapd
drwxr-xr-x 2 root root 3 Apr 29 2018 ubuntu-advantage-tools
/var/spool 上的 ls -la 的输出
$ ls -la
total 11
drwxr-xr-x 5 root root 5 May 4 12:26 .
drwxr-xr-x 15 root root 17 Apr 27 2018 ..
drwxr-xr-x 3 root root 3 May 4 12:26 cron
drwx--x--- 3 root lp 3 May 4 12:26 cups
drwx------ 2 syslog adm 2 May 4 12:21 rsyslog
答案1
您需要mountpoint从数据集中删除冗余、未使用的属性。如果rpool（根数据集）实际上未使用，则删除该mountpoint属性并将其设置在实际使用的数据集上（rpool/ROOT/ubuntu）：
zfs set mountpoint=none rpool
最重要的是，你应该rootfs除了mountpoint=/在数据集级别设置之外，还要设置zpool 属性：
zpool set bootfs=rpool/ROOT/ubuntu rpool
此外，删除挂载点目录也是安全的（ZFS 将在挂载时创建它们）。请重命名或备份这些目录。
如果您没有救援磁盘，您可以通过在启动命令行参数中添加init=/bin/Busybox sh和删除参数来获取 Busybox shell。然后，您可以导入池而不安装（ ），然后根据需要编辑属性。root=zpool import -R /mnt -n rpool
最后，绝不依靠 fstab 来挂载 zfs文件系统数据集（除了 zvols 之外swap），除非您知道自己在做什么，因为具有标准mountpoint属性的数据集会提前挂载。使用mountpoint=legacy允许使用mount或 通过 进行挂载fstab。