mysql不知道初始化密碼？

systemctl stop mysqld
systemctl set-environment MYSQLD_OPTS="--skip-grant-tables"
systemctl start mysqld
mysql -u root
mysql> UPDATE mysql.user SET authentication_string = PASSWORD('MyNewPassword') WHERE User = 'root' AND Host = 'localhost';
mysql> FLUSH PRIVILEGES;
systemctl stop mysqld
systemctl unset-environment MYSQLD_OPTS
systemctl start mysqld
mysql -u root -p