[SOLVED] How to Enable or disable Maintenance Mode using Drush in Drupal 9

Steps for Enabling or disabling maintenance mode using Drush
1. Run the following Drush commands to enable maintenance mode and clear
 

drush state:set system.maintenance_mode 1
drush cr

2.Run the following Drush commands to disable maintenance mode and clear the cache:

drush state:set system.maintenance_mode 0 
drush cache:rebuild

After running either set of commands, verify that your site is either in or out of maintenance mode by visiting the site in a browser where you are not logged in.

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References

https://www.drupal.org/docs/user_guide/en/extend-maintenance.html

https://drupal.stackexchange.com/questions/16/how-to-take-a-site-offline-using-drush