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 :