Plesk shows SQLSTATE[HY000] [2002] No such file or directory on Linux: InnoDB: Unable to lock ./ibdata1 error: 11

Symptoms

• Plesk inaccessible with the following error:

  ERROR: Zend_Db_Adapter_Exception: SQLSTATE[HY000] [2002] No such file or directory (Abstract.php:144)

• In MySQL log /var/log/mysql/error.log or /var/log/mariadb/mariadb.log the following error occurs on attempt to start/stop mysql or MariaDB service:

  [ERROR] InnoDB: Unable to lock ./ibdata1 error: 11
  [Note] InnoDB: Check that you do not already have another mysqld process using the same InnoDB data or log files.

Cause

File ./ibdata1 locked by another mysql process.

Resolution

1. Connect to the server using SSH.

2. Stop all possible MySQL services (mysql, mysqld, mariadb):

   # service mysqld stop && service mysql stop && service mysqld stop

3. Kill all MySQL processes:

   # killall -vw mysql
   # killall -vw mysqld

4. Start MySQL service:

   # service mariadb start && service mysql start && service mysqld start