Incus Zvol backup script

gistfile1.txt

```
#!/bin/bash

# Custom ZFS snapshot + sync + prune script
# By KpuCko (updated by ChatGPT)

# CONFIGURATION
ZVOLS=(
  "zpool-nvme-01/.ix-virt/custom/default_vm-100-disk-0"
  "zpool-nvme-01/.ix-virt/custom/default_vm-100-disk-1"
  "zpool-nvme-01/.ix-virt/custom/default_vm-101-disk-0"
  "zpool-nvme-01/.ix-virt/custom/default_vm-106-disk-0"
  "zpool-nvme-01/.ix-virt/custom/default_vm-109-disk-0"
  "zpool-nvme-01/.ix-virt/custom/default_vm-111-disk-0"
  "zpool-nvme-01/.ix-virt/custom/default_vm-111-disk-1"
  "zpool-nvme-01/.ix-virt/custom/default_vm-117-disk-0"
  "zpool-nvme-01/.ix-virt/custom/default_vm-117-disk-1"
  "zpool-nvme-01/.ix-virt/custom/default_vm-118-disk-0"
)
DEST_POOL="zpool-hdd-01"
SNAP_PREFIX="custom"
RETENTION=7

# FUNCTIONS
log() {
  echo "[$(date '+%Y-%m-%d %H:%M:%S')] $1"
}

# MAIN LOOP
for ZVOL in "${ZVOLS[@]}"; do
  # Extract components
  SRC_POOL="${ZVOL%%/*}"
  REL_PATH="${ZVOL#*/}"
  DEST_ZVOL="${DEST_POOL}/${REL_PATH}"
  SRC="${SRC_POOL}/${REL_PATH}"
  DST="${DEST_POOL}/${REL_PATH}"

  # Create snapshot
  SNAP_NAME="${SNAP_PREFIX}-$(date '+%Y%m%d%H%M%S')"
  SRC_SNAP="${ZVOL}@${SNAP_NAME}"
  log "Creating snapshot: $SRC_SNAP"
  zfs snapshot "$SRC_SNAP"

  # Ensure destination ZVOL exists
  if ! zfs list "$DEST_ZVOL" &>/dev/null; then
    log "Destination ZVOL $DEST_ZVOL does not exist, creating it..."
    VOLSIZE=$(zfs get -H -o value volsize "$ZVOL")
    zfs create -V "$VOLSIZE" "$DEST_ZVOL"
  fi

  # Find latest common snapshot
  SRC_SNAPS=$(zfs list -H -t snapshot -o name -s creation | grep "^${ZVOL}@${SNAP_PREFIX}-" | awk -F@ '{print $2}')
  DST_SNAPS=$(zfs list -H -t snapshot -o name -s creation | grep "^${DEST_ZVOL}@${SNAP_PREFIX}-" | awk -F@ '{print $2}')
  COMMON_SNAP=""
  for SNAP in $(echo "$SRC_SNAPS" | tac); do
    if echo "$DST_SNAPS" | grep -qx "$SNAP"; then
      COMMON_SNAP="$SNAP"
      break
    fi
  done

  # Perform send
  if [[ -n "$COMMON_SNAP" && "$COMMON_SNAP" != "$SNAP_NAME" ]]; then
    log "Incremental send from snapshot ${ZVOL}@${COMMON_SNAP} to ${ZVOL}@${SNAP_NAME} → destination ${DEST_ZVOL}"
    zfs send -c -i "${ZVOL}@${COMMON_SNAP}" "${ZVOL}@${SNAP_NAME}" | zfs receive -F "$DEST_ZVOL"
  else
    log "No common snapshot found or identical name, performing full send: ${ZVOL}@${SNAP_NAME} → destination ${DEST_ZVOL}"
    zfs send -c "${ZVOL}@${SNAP_NAME}" | zfs receive -F "$DEST_ZVOL"
  fi
  
  # Prune old snapshots on source
  log "Pruning old snapshots on source: $SRC"
  SRC_SNAPS_LIST=$(zfs list -H -t snapshot -o name -s creation | grep "^${SRC}@${SNAP_PREFIX}-")
  SNAP_COUNT=$(echo "$SRC_SNAPS_LIST" | grep -c .)
  if [ "$SNAP_COUNT" -gt "$RETENTION" ]; then
    echo "$SRC_SNAPS_LIST" | head -n -"$RETENTION" | while read -r OLD_SNAP; do
      log "Destroying old source snapshot: $OLD_SNAP"
      zfs destroy "$OLD_SNAP"
    done
  fi

  # Prune old snapshots on destination
  log "Pruning old snapshots on destination: $DST"
  DST_SNAPS_LIST=$(zfs list -H -t snapshot -o name -s creation | grep "^${DST}@${SNAP_PREFIX}-")
  SNAP_COUNT=$(echo "$DST_SNAPS_LIST" | grep -c .)
  if [ "$SNAP_COUNT" -gt "$RETENTION" ]; then
    echo "$DST_SNAPS_LIST" | head -n -"$RETENTION" | while read -r OLD_SNAP; do
      log "Destroying old destination snapshot: $OLD_SNAP"
      zfs destroy "$OLD_SNAP"
    done
  fi

done

log "All done."
```