1.这个故障出现在 MySQL 8.0 上，用戶使用 mysql client 5.6.68 连接 MySQL 8.0 提示如下

[root@VM-centos ~]# mysql -h127.0.0.1 -P6607 -uroot -p
Enter password: 
ERROR 2059 (HY000): Authentication plugin 'sha256_password' cannot be loaded: /usr/lib64/mysql/plugin/sha256_password.so: cannot open shared object file: No such file or directory

2.查看客户端工具的版本：

[root@VM-16-3-centos ~]# mysql -V
mysql  Ver 15.1 Distrib 5.5.68-MariaDB, for Linux (x86_64) using readline 5.1

3.重新安装mysql8.0

##把之前的mysql 卸载
[root@VM-16-3-centos ~]# yum remove mysql

#因为我的是centos 系统 所以用加载源的方式
[root@VM-16-3-centos ~]# cat /etc/yum.repos.d/mysql.repo
[mysql-8.0-community]
name=MySQL 8.0 Community Server
baseurl=https://mirrors.tuna.tsinghua.edu.cn/mysql/yum/mysql-8.0-community-el7-$basearch/
enabled=1
gpgcheck=1
gpgkey=https://repo.mysql.com/RPM-GPG-KEY-mysql
[root@VM-16-3-centos ~]# 

[root@VM-16-3-centos ~]# yum clean all
[root@VM-16-3-centos ~]# yum repolist

[root@VM-16-3-centos ~]# yum list | grep mysql

[root@VM-16-3-centos ~]# yum -y install mysql-community-client.x86_64

4.测试连接

[root@VM-16-3-centos ~]# mysql -P6607 -umysql_develop -p -h127.0.0.1
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 17
Server version: 8.0.23 MySQL Community Server - GPL

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql_database     |
+--------------------+
2 rows in set (0.01 sec)