move_lxd_container.sh

#!/usr/bin/env bash
set -euo pipefail

# moving all stopping LXD container from node to node.

function get_stopping_containers() {
  lxc list --format json |
    jq -rc 'map({"name": .name, "node": .location, "status": .state.status, "disk_limit": .expanded_devices.root.size, "disk_usage": .state.disk.root.usage} |
      select(.status == "Stopped" and .node == '\""$1"\"')) |
      .[]'
}

function check_disk_limit() {
  local limit
  local flag=0
  limit=$(echo "$1" | jq -r .disk_limit)
  if [ "$limit" != 'null' ]; then

    local prefix=${limit: -2}
    limit=${limit/%??/}

    case $prefix in
      "MB" ) prefix=2 ;;
      "GB" ) prefix=3 ;;
      "TB" ) prefix=4 ;;
      * ) prefix=0
          flag=1 ;;
    esac

    local usage
    usage=$(echo "$1" | jq -r .disk_usage)
    usage=$((usage/(1000**prefix)))

    if [ "$usage" -ge "$limit" ]; then
      flag=1
    fi
  fi

  echo "$flag"
}

export SRC_HOST=$1
export DST_HOST=$2
export CONTAINER_NAME

echo "Starting to move All stopping containers on $SRC_HOST to $DST_HOST..."

get_stopping_containers "$SRC_HOST" |
  while read -r container; do

    CONTAINER_NAME=$(echo "$container" | jq -r .name)

    case "$(check_disk_limit "$container")" in
      0 ) echo "Starting to move $CONTAINER_NAME to $DST_HOST..."
          lxc move "$CONTAINER_NAME" "$CONTAINER_NAME" --target "$DST_HOST"
          echo 'Done.' ;;
      1 ) echo "Can't pass disk limit check! Skipping $CONTAINER_NAME..." ;;
      * ) echo "Something went wrong! Skipping $CONTAINER_NAME..." ;;
    esac
  done

echo "All stopping containers on $SRC_HOST have been moved to $DST_HOST. Exit..."

Now we should use lxc cluster evacuate "$SRC_HOST" to maintain the node with LXD 5.0 or higher.
read the doc: https://linuxcontainers.org/lxd/docs/master/clustering/#evacuating-and-restoring-cluster-members