Why doesn't 'drush cc all' work? I installed Drush, but most of the commands doesn't work, I guess. I tried drush cc all and got the following output:


  Command cache-clear needs a higher bootstrap level to run - you will need invoke drush from a more functional Drupal environment to run this command.
  The drush command 'cc all' could not be executed.
  A Drupal installation directory could not be found                                                               


drush status outputs the following: 


  PHP configuration     :  /etc/php5/cli/php.ini
  Drush version         :  4.5
  Drush configuration   :
  Drush alias files     :
You need to rebuild cache with Drupal 8, rather than clear it:

drush cr