Symptoms

• Unable to start the mariadb/mysql service after an upgrade with the following error message in service's error log in /var/log/mariadb/mariadb.log or /var/log/mysql/error.log:

  CONFIG_TEXT: [Note] InnoDB: Starting shutdown...
  [ERROR] Plugin 'InnoDB' init function returned error.
  [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
  [Note] Plugin 'FEEDBACK' is disabled.
  [ERROR] Unknown/unsupported storage engine: InnoDB
  [ERROR] Aborting

  The same error may appear during Plesk upgrade or update

• Plesk is not accessible with:

  PLESK_ERROR: ERROR: Plesk\Exception\Database: DB query failed: SQLSTATE[HY000]: General error: 1 Can't create/write to file '/var/tmp/#sql_5f1_0.MAI' (Errcode: 2), query was: DESCRIBE `sessions`
  Additionally, an exception has occurred while trying to report this error: Zend_Exception
  No entry is registered for key 'translate' (Mysql.php:53)

Cause

The mariadb/mysql service was not stopped properly after an upgrade.

Resolution

1. Connect to the server via SSH.

2. Stop the service properly using the command::

   # mysqladmin -uadmin -p`cat /etc/psa/.psa.shadow` -h127.0.0.1 --protocol=tcp shutdown

3. Start the mariadb/mysql service using one of the command below:

   # service mariadb restart
   
   # service mysql restart
   
   # service mysqld restart