From b1c22eef0689a84c29ccbee2464b16818e5d8c6a Mon Sep 17 00:00:00 2001
From: Max Christian Pohle
Date: Sun, 3 Nov 2019 22:06:34 +0100
Subject: Added script to flatten a dataset hierachy

---
 zfs-flatten.sh | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 zfs-flatten.sh

diff --git a/zfs-flatten.sh b/zfs-flatten.sh
new file mode 100644
index 0000000..179048c
--- /dev/null
+++ b/zfs-flatten.sh
@@ -0,0 +1,67 @@
+DATASET_ROOT=$1
+DATASET_TARGET=$2
+
+MOUNTPOINT_TARGET=$(zfs get -H mountpoint -o value $DATASET_TARGET)
+
+if ! test -d "$MOUNTPOINT_TARGET"; then
+    echo "Please run this program with a source and a target dataset name as arguments"
+    echo "e.g. $0 zpool/dataset1 zpool/dataset2"
+    exit
+fi
+
+# make sure, that ctrl-c also works in the inner loops
+trap exit INT
+
+# recursively contains all snapshot names (the part after the @) from root on, sorted and only once
+SNAPSHOTS=$(zfs list -H -r $DATASET_ROOT -oname -tsnap | cut -d@ -f2 | sort  | uniq)
+DATASETS=$(zfs list -H -r $DATASET_ROOT -oname -t filesystem)
+
+echo "We are going to flatten the hierachy of this dataset:"
+printf "    %s\n" $DATASETS
+echo "into the dataset with the name:"
+echo "    $DATASET_TARGET"
+echo "mounted under:"
+echo "    $MOUNTPOINT_TARGET"
+echo ""
+echo "You have 10 seconds to abort this with CTRL-C"
+sleep 10
+
+for SNAPSHOT in $SNAPSHOTS; do
+    echo ""
+    echo ""
+    echo "==========================="
+    echo "Next snapshot is: $SNAPSHOT"
+    echo "==========================="
+
+    for DATASET in $DATASETS; do
+
+        MOUNTPOINT=$(zfs get -H mountpoint -o value $DATASET)
+
+        if [[ $MOUNTPOINT == "legacy" ]]; then
+            MOUNTPOINT=$(findmnt -n -o target $DATASET)
+            if test -d $MOUNTPOINT; then
+                >&2 echo "Dataset has a legacy mountpoint, but was not found in the fstab: $DATASET"
+                continue
+            fi
+        fi
+
+        if [[ $MOUNTPOINT == "-" ]]; then
+            >&2 echo "Dataset does not have a mount point or is a vdev: $DATASET"
+            continue
+        fi
+
+        SNAPDIR=$(realpath $MOUNTPOINT/.zfs/snapshot/$SNAPSHOT)
+        if test -d $SNAPDIR; then
+            TARGET_DIR="$(realpath $DATASET_TARGET)$(realpath $MOUNTPOINT)"
+            mkdir -p "$TARGET_DIR"
+            echo rsync --info=stats3 -a "$SNAPDIR/" "$TARGET_DIR/"
+            if ! rsync --info=stats3 -a "$SNAPDIR/" "$TARGET_DIR/" ; then
+                >&2 echo "rsync could not entirely copy from $SNAPDIR to $DATASET_TARGET"
+            fi
+        fi
+    done
+    NEW_SNAPSHOT="$DATASET_TARGET@$SNAPSHOT"
+    echo "Files copied, creating snapshot: $NEW_SNAPSHOT"
+    zfs snap $NEW_SNAPSHOT
+done
+
-- 
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