Drupal drush

Drush is a command line shell and Unix scripting interface for Drupal. Drush core ships with lots of useful commands and generators. Similarly, it runs update.php, executes SQL queries, runs content migrations, and misc utilities like cron or cache rebuild. Drush can be extended by 3rd party commandfiles.

Using Drush to rebuild or clear the cache

Use the command drush cache:rebuild to clear and rebuild all cached data for a site. After running this command, you will see the output message "Cache rebuild complete."

Use the command drush cache:clear to see a list of individual caches and then choose the specific cache you would like to clear. Running this command should produce output like the following:

> drush cache:clear

Enter a number to choose which cache to clear.

 [0]  :  Cancel

 [1]  :  drush

 [2]  :  theme-registry

 [3]  :  menu

 [4]  :  css-js

 [5]  :  block

 [6]  :  module-list

 [7]  :  theme-list

 [8]  :  render

 [9]  :  views

put your site in maintenance mode

drush eval 'variable_set('site_offline', 1)'

and to put it back on line

drush eval 'variable_set('site_offline', 0)'