Explaining shadow copies.

Samba.md

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+Make ZFS Snapshots work with Samba as Windows Shadow Copies
+===========================================================
+
+You may expose snapshots to Windows users as *shadow copies* via Samba's [vfs_shadow_copy2](https://www.samba.org/samba/docs/man/manpages/vfs_shadow_copy2.8.html).
+
+Install `zfs-auto-snapshot`
+---------------------------
+
+Some changes need to be made to `zfs-auto-snapshot` first for proper snapshot naming (see [issues/10](/zfsonlinux/zfs-auto-snapshot/issues/10) and [pull/22](/zfsonlinux/zfs-auto-snapshot/pull/22)). 
+
+    $ cd /usr/src (or wherever you want to build the .deb)
+    $ git clone https://github.com/zfsonlinux/zfs-auto-snapshot.git
+    $ git checkout leecallen
+    $ git merge master
+    $ editor src/zfs-auto-snapshot.sh (manually fix a conflict)
+    $ git add .
+    $ git commit -a
+
+Then continue using `make install` or `dpkg-buildpackage ...` if you're on Debian as explained [here](Debian).
+
+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
+        shadow: format = zfs-auto-snap_%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.