Unable to access Plesk panel: ERROR: 500 PleskExceptionDatabase: SQLSTATE[HY000] [2002] Connection refused

Symptoms

• Plesk panel is inaccessible with the error:

  500 PleskExceptionDatabase
  DB query failed: "SET sql_mode = ''" Error: SQLSTATE[HY000] [2002] Connection refused

• MariaDB service is down and fails to start.

• The log /var/log/mariadb/mariadb.log contains the following:

  [ERROR] mariadbd: Can't create/write to file '/run/mariadb/mariadb.pid' (Errcode: 2 "No such file or directory")
  [ERROR] Can't start server: can't create PID file: No such file or directory

Cause

The directory /var/run/mariadb does not exist.

Resolution

1. Log into Plesk

2. Create the missing directory:

   # mkdir /var/run/mariadb

3. Set the correct permissions

   # chown -R mysql:mysql /var/run/mariadb/

4. Start MariaDB

   # systemctl restart mariadb