SMB Previous Versions empty on 25.10.7: shadow_copy_zfs "Failed to get snapshot list" (NT_STATUS_UNSUCCESSFUL on @GMT path)

TrueNAS General
1

Hi all,

on TrueNAS SCALE 25.10.7, the “Previous Versions” tab in Windows is always empty for my SMB shares, even though periodic snapshots are created and readable. Restarting the SMB service did not help.

Setup

  • TrueNAS SCALE 25.10.7
  • Pool “daten”, datasets daten/data/manuel, daten/data/orga (and others), each shared separately via SMB
  • Periodic Snapshot Task on daten/data: recursive, hourly, lifetime 2 days, naming schema auto-%Y-%m-%d_%H-%M
  • Dataset ACL type: nfsv4 (aclmode restricted), snapdir visible
  • Pool is healthy (zpool status -x), ~1250 snapshots in total

What works

  • Snapshots exist for the datasets, e.g. daten/data/manuel@auto-2026-10-02_17-00
  • They are readable on the filesystem: ls /mnt/daten/data/manuel/.zfs/snapshot/auto-2026-10-02_17-00 lists the files
  • testparm shows shadow_copy_zfs loaded for the shares:
    vfs objects = streams_xattr shadow_copy_zfs ixnas zfs_core io_uring

What fails
Accessing a snapshot via the @GMT path fails, both from Windows and locally with smbclient. The timestamp comes from the snapshot’s creation time:

date -u -d @$(zfs get -Hp -o value creation daten/data/orga@auto-2026-10-02_17-00) +“@GMT-%Y.%m.%d-%H.%M.%S”
→ @GMT-2026.10.02-15.00.00

smbclient //127.0.0.1/orga -U <user> -c 'ls @GMT-2026.10.02-15.00.00/*'

→ NT_STATUS_UNSUCCESSFUL listing @GMT-2026.10.02-15.00.00*

Same result for the share “manuel”, so it is not specific to one dataset.

/var/log/samba4/log.smbd shows on each attempt:

vfs_shadow_copy_zfs.c:743(zfs_lookup_snapshot_list)
zfs_lookup_snapshot_list: [shadow_copy_zfs_open()]: Failed to get snapshot list for /mnt/daten/data/manuel
zfs_lookup_snapshot_list: [zfs_parent_pathname()]: Failed to get snapshot list for /mnt/daten/data/manuel

Already checked

  • Snapshot names match the default auto- schema; no other snapshot names in daten/data
  • Share paths point to the dataset roots, no nested child datasets
  • SMB service restarted
  • Windows side not the cause: the error appears with smbclient directly on the NAS

Is this a known issue in 25.10.x? Is there anything else I can check (e.g. debug logging for shadow_copy_zfs)? I can provide a debug file if needed.

Thanks!

2

What is setting for zfs snapdir? Due to some risks with certain clients we have to be somewhat careful how we surface snapshots.

3

Thanks for the reply. snapdir is set to “visible” on all datasets in question. It is inherited from the parent dataset daten/data:

NAME PROPERTY VALUE SOURCE
daten/data/manuel snapdir visible inherited from daten/data

I did not set it deliberately for the SMB shares, it has probably been like that since I created the datasets. I can switch it to “hidden” and test again if that helps.

4

Set it to hidden and restart SMB service