pkill -9 mysqld  
  rpm -qa|grep -i mysql 

  yum -y remove mysql-community-client-5.6.38-2.el7.x86_64

 [root@localhost ~]# cd /usr/local/src/
 [root@localhost src]# wget http://repo.mysql.com/mysql57-community-release-el7-8.noarch.rpm
 [root@localhost src]# rpm -ivh mysql57-community-release-el7-8.noarch.rpm
 [root@localhost src]# yum -y install mysql-server

[mysqld]
 #
 # Remove leading # and set to the amount of RAM for the most important data
 # cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
 # innodb_buffer_pool_size = 128M
 #
 # Remove leading # to turn on a very important data integrity option: logging
 # changes to the binary log between backups.
 # log_bin
 #
 # Remove leading # to set options mainly useful for reporting servers.
 # The server defaults are faster for transactions and fast SELECTs.
 # Adjust sizes as needed, experiment to find the optimal values.
 # join_buffer_size = 128M
 # sort_buffer_size = 2M
 # read_rnd_buffer_size = 2M
 datadir=/var/lib/mysql
 socket=/var/lib/mysql/mysql.sock
 server_id = 1
 expire_logs_days = 3
 # Disabling symbolic-links is recommended to prevent assorted security risks
 symbolic-links=0
 log-error=/var/log/mysqld.log
 pid-file=/var/run/mysqld/mysqld.pid

 [root@localhost ~]# grep "password" /var/log/mysqld.log 

alter user 'root'@'localhost' identified by 'Root!!2018'; 

 CREATE USER ‘root‘@‘%‘ IDENTIFIED BY ‘您的密码‘;

 grant all on *.* to 'root001'@'%' identified by 'Root@@' with grant option;

重新启动mysqld
 #/etc/init.d/mysqld restart ( service mysqld restart )
 use mysql 
 update user set password=password("12345") where user="root";
 mysql 5.7的数据库没有了password字段 用的是authentication_string字段
mysql> update mysql.user set authentication_string=password('root') where user='root' ;
 flush privileges;