Assuming you have a downloaded file for which you wish to check the sha256 fingerprint do, in the commandline navigate to the downloaded file and do:

certUtil -hashfile <filename> sha256

Helper function to relocate container/vm to a new storage backend on the same host:

function MoveContainerStorage() {
  container="$1"
  newBackend="$2"
  lxc stop "$container"
  lxc move "${container}" "${container}-tmp" -s "$newBackend"
  lxc move "${container}-tmp" "${container}"
  lxc start "${container}"
}