Samba

Make ZFS Snapshots work with Samba as Windows Shadow Copies

⚠️ Update: Starting with Samba 4.5.0 and higher, Samba can be made more permissive in snapshot names it accepts. For those versions it should be easier to only adjust Samba and **no longer necessary adjusting the snapshot names** themselves as explained below. (Cf. new Samba options `shadow:snapprefix` and `shadow:delimiter`.) Try the following:

   vfs objects = shadow_copy2
   shadow: snapdir = .zfs/snapshot
   shadow: sort = desc
   shadow: format = -%Y-%m-%d-%H%M
   shadow: snapprefix = ^zfs-auto-snap_\(frequent\)\{0,1\}\(hourly\)\{0,1\}\(daily\)\{0,1\}\(monthly\)\{0,1\}
   shadow: delimiter = -20

• You may expose snapshots to Windows users as shadow copies via Samba's vfs_shadow_copy2.

Install zfs-auto-snapshot

Some changes need to be made to zfs-auto-snapshot first for proper snapshot naming (see issues/10 and pull/22).

$ cd /usr/src (or wherever you want to build the .deb)
$ git clone https://github.com/zfsonlinux/zfs-auto-snapshot.git
$ cd zfs-auto-snapshot
$ git merge origin/leecallen
$ editor src/zfs-auto-snapshot.sh (manually fix some code conflicts and change `sh` to `bash` first line)
$ git add .
$ git commit -a

Then continue using make install or dpkg-buildpackage ... if you're on Debian as explained here.

Configure ZFS

After making the above changes, zfs-auto-snapshot honors a ZFS property defining where snapshots are created and where not. Set the property accordingly:

$ zfs set com.sun:auto-snapshot=true tank/data
$ zfs set com.sun:auto-snapshot=false tank/var

NB: The snapdir .zfs/snapshot may remain hidden and Samba can still access them. Optionally hide them (from ls, etc.) using $ zfs set snapdir=hidden tank

Configure Samba

To expose shadow copies to Windows users, Samba needs its vfs_shadow_copy2 module.

On Debian do:

$ apt-get install samba-vfs-modules

Then configure smb.conf by configuring your shares:

[global]
    shadow: snapdir = .zfs/snapshot
    shadow: sort = desc
    # Specify snapshot name: frequent, hourly, daily... as desired
    shadow: format = zfs-auto-snap_frequent-%Y-%m-%d-%H%M

[myshare]
    path = /my/tank/data
    read only = No
    comment = ZFS dataset with Previous Versions enabled
    vfs objects = shadow_copy2

On Windows

On Windows check the "Previous Versions" of your share. There should be new elements in the list after some automatic snapshots are created by cron.