Plesk installation fails: Failed to execute operation: Too many levels of symbolic links

Symptoms

• Unable to  install Plesk with the following error::

  PLESK_INFO: Synchronizing state of mysql.service with SysV init with /lib/systemd/systemd-sysv-install…
  Executing /lib/systemd/systemd-sysv-install enable mysql
  Failed to execute operation: Too many levels of symbolic links

• Both MariaDB and MySQL services are running on the server:

  # systemctl status mariadb
  …
  Active: active (running) since Tue 2018-04-17 00:31:39 CEST; 1min 47s ago
  Apr 17 00:31:39 3-lithium mysqld[11431]: Version: ‘10.3.6-MariaDB-1:10.3.6+maria~xenial-log’ socket: ‘/var/run/mysqld/mysqld.sock‘ port: 3306 mariadb.org binary distribution

  # systemctl status mysqld
  …
  Active: active (running) since Tue 2018-04-17 00:31:39 CEST; 2min 9s ago
  Apr 17 00:31:39 3-lithium mysqld[11431]: Version: ‘10.3.6-MariaDB-1:10.3.6+maria~xenial-log’ socket: ‘/var/run/mysqld/mysqld.sock‘ port: 3306 mariadb.org binary distribution

• As can be seen from the output of the commands above services are using the same binary file of MariaDB:

  10.3.6-MariaDB-1:10.3.6+maria~xenial-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 mariadb.org binary distribution

Cause

MariaDB and MySQL services are using the same MariaDB binary file.

Resolution

1. Log into the server via SSH.

   Note: If direct SSH access to the server is not possible, contact server administrator for further assistance.

2. Stop MariaDB service:

   # systemctl stop mariadb

3.  Disable MariaDB service:

   # systemctl disable mariadb

4.  Delete existing symlinks of MariaDB and MySQL services:

   # rm /etc/systemd/system/mariadb.service

5.  Enable MariaDB service:

   # systemctl enable MariaDB:

6.  Start Mariadb:

   # systemctl start mariadb