From acef33b4d5d374c4a2b4377471efd173f8db9a2e Mon Sep 17 00:00:00 2001
From: Jochen Welzel <jochen.welzel@de.clara.net>
Date: Wed, 6 Jan 2021 10:29:58 +0100
Subject: [PATCH] add incremental send

---
 libvirt-zsh-backup.sh | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libvirt-zsh-backup.sh b/libvirt-zsh-backup.sh
index efd58a2..9dcbd36 100644
--- a/libvirt-zsh-backup.sh
+++ b/libvirt-zsh-backup.sh
@@ -73,7 +73,15 @@ done
 
 virsh snapshot-delete $VM $SNAPNAME --metadata
 
-zfs send "$SRCZFS"@"$SNAPNAME" | pv -L 500M | ssh $DESTHOST sudo zfs recv -F $DESTZFS
+SUCCESS=$(zfs get backup:success -H -o value $SRCZFS)
+if [[ $SUCCESS == "true" ]]
+then
+    LASTBACKUP=$(zfs get backup:date -H -o value $SRCZFS)
+    LASTSNAP="backup_$LASTBACKUP"
+    zfs send -i "$SRCZFS"@"$LASTSNAP" "$SRCZFS"@"$SNAPNAME" | pv -L 500M | ssh $DESTHOST sudo zfs recv -F $DESTZFS
+else
+    zfs send "$SRCZFS"@"$SNAPNAME" | pv -L 500M | ssh $DESTHOST sudo zfs recv -F $DESTZFS
+fi
 if [ $? -eq 0 ]
 then
     zfs set backup:success="true" $SRCZFS