Plesk upgrade failed: /usr/bin/mysql: unknown variable

Symptoms

• The following is shown in /var/log/plesk/install/plesk_18.0.*_installation.log:

/usr/bin/mysql: unknown variable 'sql_mode=ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'

• Attempt to query MySQL version fails the same errors:

# mysql -V
/usr/bin/mysql: unknown variable ‘sql_mode=ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION’

Cause

Deprecated MySQL variables are specified in /etc/my.cnf:

ERROR_FOR_DIVISION_BY_ZERO is set by default since MySQL 10.2.4
NO_AUTO_CREATE_USER is also deprecated

Resolution

2. Remove deprecated variables from the config file: /etc/my.cnf. For Ubuntu/Debian only: remove it from all files within /etc/mysql directory.

3. Restart MySQL service:

# systemctl restart mariadb || systemctl restart mysqld