From bc90f87636f065bfdec6018eb83263dcb3508c08 Mon Sep 17 00:00:00 2001
From: Alice Gaudon <alice@gaudon.pro>
Date: Fri, 13 Nov 2020 11:06:19 +0100
Subject: [PATCH] Make zfs backups resumable and more improvements

---
 zfs_backup.sh         | 34 +++++++++-------
 zfs_backup_dataset.sh | 94 ++++++++++++++++++++++++++-----------------
 2 files changed, 78 insertions(+), 50 deletions(-)

diff --git a/zfs_backup.sh b/zfs_backup.sh
index c97191d..fdaf207 100755
--- a/zfs_backup.sh
+++ b/zfs_backup.sh
@@ -1,11 +1,5 @@
 #!/bin/sh
 
-if ! lockfile-create -p -r 2 $0; then
-	echo "Another backup is running, aborting"
-	exit 49
-fi
-
-
 ### Arguments ###
 DATASET=$1
 if test -z "$DATASET"; then
@@ -40,21 +34,33 @@ fi
 SNAPSHOT="$DATASET@$NAME"
 PREVIOUS_SNAPSHOT="$DATASET@$PREVIOUS_NAME"
 REMOTE_NAME="$TARGET_PATH/"$(echo -e $DATASET | sed -r "s/\//_/g")
+LOCK_NAME="${0}_"$(echo -e $DATASET | sed -r "s/\//_/g")
+
+### LOCK ###
+if ! lockfile-create -p -r 2 $LOCK_NAME; then
+	echo "Another backup is running, aborting"
+	exit 49
+fi
 
 
-# Take snapshot
-echo "Creating $SNAPSHOT snapshot..."
-zfs snapshot $SNAPSHOT || exit 1
-echo "Snapshot created."
+# Create snapshot
+exists=$(zfs list -H -t snapshot -o name $SNAPSHOT)
+if [ "$exists" = "$SNAPSHOT" ]; then
+	echo "Snapshot $SNAPSHOT already exists, skip create."
+else
+	echo "Creating $SNAPSHOT snapshot..."
+	zfs snapshot $SNAPSHOT || exit 1
+	echo "Snapshot created."
+fi
 
 # Send snapshot
 echo "Sending snapshot ($PREVIOUS_SNAPSHOT --- $SNAPSHOT) to $REMOTE_NAME ..."
 if test ! -z "$PREVIOUS_NAME"; then
 	incr="-I $PREVIOUS_SNAPSHOT"
 fi
-zfs send -v -p $incr $SNAPSHOT | ssh $TARGET zfs receive -F $REMOTE_NAME || exit 1
+zfs send -v -p $incr $SNAPSHOT | ssh $TARGET zfs receive -F -s $REMOTE_NAME || exit 1
 echo "Snapshot sent."
 
-# Remove lock
-echo "Backup finished. Removing lock..."
-lockfile-remove $0
+### UNLOCK ###
+echo "Backup of $DATASET dataset finished. Removing lock..."
+lockfile-remove $LOCK_NAME
diff --git a/zfs_backup_dataset.sh b/zfs_backup_dataset.sh
index e178cec..aee921d 100755
--- a/zfs_backup_dataset.sh
+++ b/zfs_backup_dataset.sh
@@ -18,52 +18,74 @@ if test -z "$TARGET_PATH"; then
 	exit 1
 fi
 
-### New snapshot ###
-NAME=$(date +%Y-%m-%d_%H-%M-%S)
-SNAPSHOT="$DATASET@$NAME"
+DATE=$4
+if test -z "$DATE"; then
+	DATE=$(date +%Y-%m-%d_%H-%M)
+fi
 
+REMOTE_NAME="$TARGET_PATH/"$(echo -e $DATASET | sed -r "s/\//_/g")
+
+
+### Resume existing transfer ###
+RESUME_TOKEN=$(ssh $TARGET zfs get -H -p receive_resume_token -o value "$REMOTE_NAME")
+if [ "$RESUME_TOKEN" != "" ] && [ "$RESUME_TOKEN" != "-" ]; then
+	echo "Resuming interrupted transfer..."
+	zfs send -v -t "$RESUME_TOKEN" | ssh $TARGET zfs receive -F -s "$REMOTE_NAME" || exit 1
+	echo "Resumed transfer finished."
+	exit 0
+fi
+
+
+### Sync existing snapshots ###
+REMOTE_SNAPSHOTS=($(ssh $TARGET zfs list -H -t snapshot -o name -s creation $REMOTE_NAME | cut -d"@" -f 2))
+LOCAL_SNAPSHOTS=($(zfs list -H -t snapshot -o name -s creation $DATASET | cut -d"@" -f 2))
+
+echo "Remote snapshots: $REMOTE_SNAPSHOTS"
+
+for local_snapshot in "${LOCAL_SNAPSHOTS[@]}"; do
+	echo "Syncing local snapshot $local_snapshot ..."
+	found=false
+	for remote_snapshot in "${REMOTE_SNAPSHOTS[@]}"; do
+		if [ "$remote_snapshot" = "$local_snapshot" ] ; then
+			found=true
+			break
+		fi
+	done
+
+	if [ $found = true ] ; then
+		echo "> Found remotely, settings as last snapshot"
+		LAST_SNAPSHOT=$local_snapshot
+		EXISTING_SNAPSHOT=""
+	else
+		echo "> Needs sync"
+		EXISTING_SNAPSHOT=$local_snapshot
+	fi
+done
+
+
+### New snapshot ###
+if [ "$EXISTING_SNAPSHOT" = "" ]; then
+	NAME=$DATE
+else
+	NAME=$EXISTING_SNAPSHOT
+fi
+SNAPSHOT="$DATASET@$NAME"
 echo "New snapshot name is: $NAME"
 echo "New snapshot is: $SNAPSHOT"
 
 
-### Default last snapshot ###
-DEFAULT_LAST_SNAPSHOT=$(zfs list -t snapshot -o name -s creation -H $DATASET | tail -n 1)
-DEFAULT_LAST_NAME=$(echo -e $DEFAULT_LAST_SNAPSHOT | rev | cut -d"@" -f1 | rev)
-echo "Default last snapshot is: $DEFAULT_LAST_SNAPSHOT"
-echo "Default last snapshot name is: $DEFAULT_LAST_NAME"
-
-
-### Tracking folder ###
-tracking_folder="$HOME/.local/share/zfs_backup"
-if test ! -d $tracking_folder; then
-	echo "Creating backup tracking files directory"
-	mkdir -p $tracking_folder
-fi
-
-
 ### Last snapshot ###
-LAST_SNAPSHOT=$DEFAULT_LAST_SNAPSHOT
-
-last_snapshot_file="$tracking_folder/last_snapshot_"$(echo -e $DATASET | sed -r "s/\//_/g")
-if test -f $last_snapshot_file; then
-	LAST_SNAPSHOT=$(cat $last_snapshot_file)
-	echo "Found $last_snapshot_file"
-else
-	echo "No $last_snapshot_file, resolving to default"
-fi
-
-LAST_SNAPSHOT_NAME=$(echo -e $LAST_SNAPSHOT | rev | cut -d"@" -f1 | rev)
-
 echo "Last snapshot is: $LAST_SNAPSHOT"
-echo "Last snapshot name is: $LAST_SNAPSHOT_NAME"
 
-echo "Starting backup with args $DATASET $NAME $LAST_SNAPSHOT_NAME"
-$HOME/scripts/zfs_backup.sh $DATASET $NAME $LAST_SNAPSHOT_NAME $TARGET $TARGET_PATH || exit 1
 
-echo "Saving new snapshot in tracking folder..."
-echo -e $SNAPSHOT > $last_snapshot_file
+## Perform transfer
+echo "Starting backup with args $DATASET $NAME $LAST_SNAPSHOT"
+$HOME/scripts/zfs_backup.sh $DATASET $NAME "$LAST_SNAPSHOT" $TARGET $TARGET_PATH || exit 1
 
+
+## Destroy last snapshot
 echo "Destroying last snapshot..."
-zfs destroy $LAST_SNAPSHOT || exit 1
+zfs destroy "$DATASET@$LAST_SNAPSHOT" || exit 1
+
 
 echo "Backup finished."