The error in Plesk: ERR [panel] SQLSTATE[HY000] [2002] No such file or directory, Can’t connect to local MySQL server through socket

Symptoms

• The following error is shown instead of the Plesk login page:

  ERR [panel] SQLSTATE[HY000] [2002] No such file or directory

• Generation of the login link fails:

  # plesk login
  ERR [panel] SQLSTATE[HY000] [2002] No such file or directory:
  0: /usr/local/psa/admin/externals/Zend/Db/Adapter/Pdo/Abstract.php:144
  ..........
  ERROR: Zend_Db_Adapter_Exception: SQLSTATE[HY000] [2002] No such file or directory (Abstract.php:144)

• It is possible to login to the Plesk configuration database (psa) using the command:

  # plesk db

• No errors can be found in the MySQL/MariaDB error log (can be located at /var/log/mysqld.log, /var/log/mariadb/mariadb.log or /var/log/mysql/error.log) even during the restart of the service.

• Manual running of the backupmng utility fails with the following error:

  # plesk sbin backupmng
  backupmng: Unable to connect to Plesk Database: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (13)
  System error 13: Permission denied
  backupmng: Unable to connect to Plesk Database: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (13)
  System error 13: Permission denied
  backupmng: Unable to connect to the mysql database

• When deleting a domain or a subscription from Plesk, the following error can be found in the file /var/log/plesk/panel.log:

  PHP Fatal error: Uncaught exception 'PleskMultipleException' with message 'Error during example.com removeZone: dnsmng failed: dnsmng: Unable to connect to Plesk Database: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
  System error 2: No such file or directory
  dnsmng: Unable to connect to the mysql database
  System error 2: No such file or directory
  in /opt/psa/admin/plib/Service/Dns/Connector/Plesk.php:14
  Stack trace:
  ..........
  thrown in /opt/psa/admin/plib/Service/Dns/Connector/Plesk.php on line 14

Cause

The sockets specified in the files /etc/psa/psa.conf and /usr/local/psa/admin/conf/php.ini differ from the actual MySQL/MariaDB socket defined in the file /etc/my.cnf (/etc/mysql/my.cnf on Debian and Ubuntu).

Resolution

1. Connect to the server using SSH.

2. Make sure that the sockets to connect to the MySQL/MariaDB server specified in the files /etc/psa/psa.conf and /usr/local/psa/admin/conf/php.ini are the same as the socket defined in the file /etc/my.cnf (/etc/mysql/my.cnf on Debian and Ubuntu):

   # grep mysql.sock /etc/my.cnf
   socket=/var/lib/mysql/mysql.sock

   # grep mysql.sock /etc/psa/psa.conf
   MYSQL_SOCKET /var/lib/mysql/mysql.sock

   # grep mysql.sock /usr/local/psa/admin/conf/php.ini
   pdo_mysql.default_socket="/var/lib/mysql/mysql.sock"