Messages about failed logrotate task are received in Plesk on Ubuntu 18 or Debian 9: 'Access denied for user 'root'@'localhost' (using password: NO)

Connect to the server via SSH

Create a backup of the initial configuration file:

# cp -a /etc/mysql/debian.cnf /root/debian.cnf

Create MySQL database backup:

# MYSQL_PWD=`cat /etc/psa/.psa.shadow` mysqldump -u admin mysql > "mysql`date +%F_%H.%M`.sql"

Access MySQL:

# plesk db

Create MySQL user root with password:

GRANT RELOAD, SHUTDOWN, PROCESS, SHOW DATABASES, SUPER, LOCK TABLES ON *.* TO 'root'@'localhost' IDENTIFIED BY 'your_password';

Exit MySQL:

exit;

Modify /etc/mysql/debian.cnf and specify user with password created above:

[client]
host = localhost
user = root
password = "your_password"
socket = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
host = localhost
user = root
password = "your_password"
socket = /var/run/mysqld/mysqld.sock
basedir = /usr

Make sure that logrotate works. If the command doesn't show the output then everything works properly:

# mysqladmin --defaults-file=/etc/mysql/debian.cnf --local flush-error-log