How to find out if your Application is using unique hash_salts between sites

Environment

• Drupal 8+
• Multi-site
• Acquia Cloud Site Factory

Objective

Unique hash_salts are required for each site in a multi-site or Site Factory environment. This unique hash_salt is sometimes referenced by backend processes. Different types of plugin errors that are difficult to track down if unique hash_salts are not defined. 

Resolution

For each site, run this Drush command and replace "example.com" with your site name. Use Drush aliases to run Drush remotely.

drush --uri=example.com php-eval 'echo \Drupal\Core\Site\Settings::getHashSalt();'

Related Content

https://docs.acquia.com/cloud-platform/manage/ssh/drush/aliases/
How to set a unique hash_salt for an individual site