ubuntu mariadb access denied for user 'root'@'localhost' code example

Example 1: access denied for user 'root'@'localhost' mariadb

UPDATE mysql.user SET plugin = 'mysql_native_password' WHERE user = 'root' AND plugin = 'unix_socket';
FLUSH PRIVILEGES;

Example 2: mariadb mysql root access denied

UPDATE mysql.user SET plugin = 'mysql_native_password' WHERE user = 'root' AND plugin = 'unix_socket';
FLUSH PRIVILEGES;