I am reinstall ghost.
Now i am import successfully zroot pool
I want umount pool but cant.

root@devuan:/# zpool export zroot
cannot unmount '/var/log': pool or dataset is busy
root@devuan:/# zfs get mountpoint
NAME                                      PROPERTY    VALUE       SOURCE
zroot                                     mountpoint  legacy      local
zroot/ROOT                                mountpoint  none        local
zroot/ROOT/25.01-backup-2025-04-29-18-27  mountpoint  /           local
zroot/ROOT/default                        mountpoint  /           local
zroot/ROOT/default@2025-04-29-18:27:42-0  mountpoint  -           -
zroot/home                                mountpoint  /home       local
zroot/tmp                                 mountpoint  /tmp        local
zroot/usr                                 mountpoint  /usr        local
zroot/usr/ports                           mountpoint  /usr/ports  inherited from zroot/usr
zroot/var                                 mountpoint  /var        local
zroot/var/audit                           mountpoint  /var/audit  inherited from zroot/var
zroot/var/crash                           mountpoint  /var/crash  inherited from zroot/var
zroot/var/log                             mountpoint  /var/log    inherited from zroot/var
zroot/var/mail                            mountpoint  /var/mail   inherited from zroot/var
zroot/var/tmp                             mountpoint  /var/tmp    inherited from zroot/var
root@devuan:/# zfs holds
usage:
	holds [-rHp] <snapshot> ...

For the property list, run: zfs set|get

For the delegated permission list, run: zfs allow|unallow

For further help on a command or topic, run: zfs help [<topic>]
root@devuan:/# zpool list -v
NAME        SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
zroot       144G  7.42G   137G        -        4G     0%     5%  1.00x    ONLINE  -
  sdb       145G  7.42G   137G        -        4G     0%  5.15%      -    ONLINE
root@devuan:/# df -h
Filesystem       Size  Used Avail Use% Mounted on
udev             1.9G     0  1.9G   0% /dev
tmpfs            392M  1.1M  391M   1% /run
/dev/sde1         71G   28G   40G  42% /
tmpfs            5.0M  8.0K  5.0M   1% /run/lock
tmpfs            1.6G     0  1.6G   0% /dev/shm
/dev/sdc3        340G  262G   61G  82% /home
zroot/tmp        133G  256K  133G   1% /tmp
zroot/usr/ports  133G  128K  133G   1% /usr/ports
zroot/var/crash  133G  128K  133G   1% /var/crash
zroot/var/audit  133G  128K  133G   1% /var/audit
zroot/var/log    133G  512K  133G   1% /var/log
tmpfs            392M   16K  392M   1% /run/user/1000
root@devuan:/# zfs umount -f zroot/var/log
cannot unmount '/var/log': pool or dataset is busy
root@devuan:/# zpool status
  pool: zroot
 state: ONLINE
status: Some supported and requested features are not enabled on the pool.
	The pool can still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
	the pool may no longer be accessible by software that does not support
	the features. See zpool-features(7) for details.
config:

	NAME        STATE     READ WRITE CKSUM
	zroot       ONLINE       0     0     0
	  sdb       ONLINE       0     0     0

errors: No known data errors
root@devuan:/#

root@devuan:/# lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
sda      8:0    0 186.3G  0 disk 
├─sda1   8:1    0  10.5G  0 part 
├─sda2   8:2    0     1K  0 part 
├─sda5   8:5    0  29.3G  0 part 
├─sda6   8:6    0  48.8G  0 part 
├─sda7   8:7    0  48.8G  0 part 
└─sda8   8:8    0  48.8G  0 part 
sdb      8:16   0   149G  0 disk 
├─sdb1   8:17   0   256K  0 part 
├─sdb2   8:18   0 144.5G  0 part 
└─sdb3   8:19   0   4.5G  0 part 
sdc      8:32   0 931.5G  0 disk 
├─sdc1   8:33   0  75.7G  0 part 
├─sdc2   8:34   0     4G  0 part 
├─sdc3   8:35   0 345.7G  0 part /home
├─sdc4   8:36   0     1K  0 part 
└─sdc5   8:37   0 506.1G  0 part 
sdd      8:48   0   149G  0 disk 
├─sdd1   8:49   0  70.3G  0 part 
├─sdd2   8:50   0   4.5G  0 part 
├─sdd3   8:51   0    50M  0 part 
└─sdd4   8:52   0  74.2G  0 part 
sde      8:64   0 223.6G  0 disk 
├─sde1   8:65   0  72.3G  0 part /
├─sde2   8:66   0  72.3G  0 part 
├─sde3   8:67   0    75G  0 part 
├─sde4   8:68   0     1K  0 part 
└─sde5   8:69   0     4G  0 part [SWAP]
sdf      8:80   1    30G  0 disk 
├─sdf1   8:81   1   800K  0 part 
└─sdf3   8:83   1   2.8G  0 part 
sr0     11:0    1  1024M  0 rom  
root@devuan:/#