> systemctl stop mysqld

> systemctl set-environment MYSQLD_OPTS="--skip-grant-tables"

> mysql -uroot

mysql> USE mysql
mysql> ALTER USER "root"@"localhost" IDENTIFIED BY "MyNewPassword";
mysql> FLUSH PRIVILEGES;
mysql> quit

> systemctl stop mysqld

> systemctl unset-environment MYSQLD_OPTS

> systemctl start mysqld

# service mysqld restart

# mysql 
mysql> USE mysql ; 
mysql> UPDATE user SET Password = password ( 'new-password' ) WHERE User = 'root' ; 
mysql> flush privileges ; 
mysql> quit

# vim /etc/my.cnf 

将刚才在[mysqld]的段中加上的skip-grant-tables删除 保存并且退出vim

# service mysqld restart