ZFS Does a dataset rollback recover a deleted directory?

[Starcat]

I'm running 14.3-STABLE.

I recursively deleted /var/cache and wanted to zfs-rollback(8) the zroot/var dataset to recover it. That didn't work, so I had to copy it back from the snapshot directory:

# zfs list -t snapshot -r zroot/var
NAME                            USED  AVAIL  REFER  MOUNTPOINT
zroot/var@143-all-epoch           0B      -    96K  -
zroot/var@143-all-x11             0B      -    96K  -
zroot/var/audit@143-all-epoch     0B      -    96K  -
zroot/var/audit@143-all-x11       0B      -    96K  -
zroot/var/crash@143-all-epoch     0B      -    96K  -
zroot/var/crash@143-all-x11       0B      -    96K  -
zroot/var/log@143-all-epoch     116K      -   164K  -
zroot/var/log@143-all-x11       124K      -   236K  -
zroot/var/mail@143-all-epoch     72K      -   104K  -
zroot/var/mail@143-all-x11        0B      -   160K  -
zroot/var/tmp@143-all-epoch      64K      -    96K  -
zroot/var/tmp@143-all-x11         8K      -    96K  -
# rm -f -r /var/cache
# ls -al /var/cache
ls: /var/cache: No such file or directory
# zfs rollback zroot/var@143-all-x11
# ls -al /var/cache
ls: /var/cache: No such file or directory
# cp -R /.zfs/snapshot/143-all-x11/var/cache /var
# ls -al /var/cache
total 195
drwxr-xr-x   5 root wheel    5 Nov  3 23:03 .
drwxr-xr-x  26 root wheel   26 Nov  3 23:03 ..
drwxr-x---   3 root wheel    3 Nov  3 23:03 cups
drwxr-xr-t   2 root wheel    2 Nov  3 23:03 gdm
drwxr-xr-x   2 root wheel 1514 Nov  3 23:03 pkg

Am I misunderstanding how a rollback is supposed to work? Any input would be appreciated. Thank you.

 

[SirDice]

the zroot/var dataset

That dataset is just a placeholder, it has no data. It's not even mounted.

% zfs list -o name,canmount,mounted,mountpoint zroot/var
NAME       CANMOUNT  MOUNTED  MOUNTPOINT
zroot/var  off       no       /var

/var/ and /var/cache are part of the BE, it'll be in zroot/ROOT/default. That said, there's nothing worth saving in /var/cache, it's cached data, it'll be recreated when needed. Just make sure the directory itself exists.