samba shadow copy cannot match

Question

The test machine is running Ubuntu server 20.04 LTS, I'm tring to expose zfs snapshots to samba share as shadow copies but failed.

Here is the smb.conf share block:

[Storage]
   comment = NAS Storage
   path = /storage/smb
   browseable = yes
   read only = no
   guest ok = no
   create mask = 0755
   directory mask = 0755
   vfs objects = shadow_copy2
   shadow:format = "CST-%Y.%m.%d-%H.%M.%S"
   shadow:localtime = yes
   shadow:snapdir = .zfs/snapshot
   ;shadow:basedir = /storage/smb

And these are zfs snapshots:

root@samba-1:/var/log/samba# zfs list -t snapshot
NAME                                  USED  AVAIL     REFER  MOUNTPOINT
storage/smb@CST-2022.03.08-23.25.35    16K      -       26K  -
storage/smb@CST-2022.03.08-23.39.39    16K      -       26K  -
storage/smb@CST-2022.03.09-00.01.17  56.5K      -     66.5K  -

And I found these in logs:

[2022/03/09 12:53:40.750713, 10, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/smbd/files.c:824(file
_name_hash)
  file_name_hash: /storage/smb//storage/smb/.zfs/snapshot hash 0xb6dc192a
[2022/03/09 12:53:40.750846, 10, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_co
py2.c:1870(shadow_copy2_snapshot_to_gmt)
  shadow_copy2_snapshot_to_gmt: no match "CST-%Y.%m.%d-%H.%M.%S": .
[2022/03/09 12:53:40.750872,  6, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_copy2.c:2064(shadow_copy2_get_shadow_copy_data)
  shadow_copy2_get_shadow_copy_data: ignoring .
[2022/03/09 12:53:40.750892, 10, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_copy2.c:1870(shadow_copy2_snapshot_to_gmt)
  shadow_copy2_snapshot_to_gmt: no match "CST-%Y.%m.%d-%H.%M.%S": ..
[2022/03/09 12:53:40.750910,  6, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_copy2.c:2064(shadow_copy2_get_shadow_copy_data)
  shadow_copy2_get_shadow_copy_data: ignoring ..
[2022/03/09 12:53:40.750928, 10, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_copy2.c:1870(shadow_copy2_snapshot_to_gmt)
  shadow_copy2_snapshot_to_gmt: no match "CST-%Y.%m.%d-%H.%M.%S": CST-2022.03.09-00.01.17
[2022/03/09 12:53:40.750947,  6, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_copy2.c:2064(shadow_copy2_get_shadow_copy_data)
  shadow_copy2_get_shadow_copy_data: ignoring CST-2022.03.09-00.01.17
[2022/03/09 12:53:40.750973, 10, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_copy2.c:1870(shadow_copy2_snapshot_to_gmt)
  shadow_copy2_snapshot_to_gmt: no match "CST-%Y.%m.%d-%H.%M.%S": CST-2022.03.08-23.39.39
[2022/03/09 12:53:40.751003,  6, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_copy2.c:2064(shadow_copy2_get_shadow_copy_data)
  shadow_copy2_get_shadow_copy_data: ignoring CST-2022.03.08-23.39.39
[2022/03/09 12:53:40.751030, 10, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_copy2.c:1870(shadow_copy2_snapshot_to_gmt)
  shadow_copy2_snapshot_to_gmt: no match "CST-%Y.%m.%d-%H.%M.%S": CST-2022.03.08-23.25.35
[2022/03/09 12:53:40.751053,  6, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/modules/vfs_shadow_copy2.c:2064(shadow_copy2_get_shadow_copy_data)
  shadow_copy2_get_shadow_copy_data: ignoring CST-2022.03.08-23.25.35
[2022/03/09 12:53:40.751112,  5, pid=3211, effective(101105, 100513), real(101105, 0)] ../../source3/smbd/files.c:636(file_free)
  freed files structure 0 (4 used)
[2022/03/09 12:53:40.751137, 10, pid=3211, effective(101105, 100513), real(101105, 0), class=vfs] ../../source3/modules/vfs_default.c:1482(vfswrap_fsctl)
  FSCTL_GET_SHADOW_COPY_DATA: 0 volumes for path[.].

why the compare is no match ? I generate the snapshot name using date +%Y.%m.%d-%H.%M.%S

Answer 1

My system is a Raspberry Pi 4 with Raspberry Pi OS lite 64bits and Samba Version 4.13.13-Debian and I'm having the same problems, but found a strange solution:

You have to set this

shadow:localtime = no

The following e-mail on the Samba mailing list gave me a clue.