系统：CentOS 7.8(2003)版本最小化安装
MySQL:8.0.21
注意，页面上没有CentOS的选项，选择RedHat 7相关的系统就行，他们之间的关系不可描述，囧。
先下载了RPM Server包，以为能够一直安装过
cd /usr/lcoal/src
wget https://..........mysql-community-server-8.0.21-1.el7.x86_64.rpm #直接去页面上找地址
rpm -ivh mysql-community-server-8.0.21-1.el7.x86_64.rpm
结果发现缺少依赖包，囧。
警告：mysql-community-server-8.0.21-1.el7.x86_64.rpm: 头V3 DSA/SHA1 Signature, 密钥 ID 5072e1f5: NOKEY
错误：依赖检测失败：
mysql-community-client(x86-64) >= 8.0.11 被 mysql-community-server-8.0.21-1.el7.x86_64 需要
mysql-community-common(x86-64) = 8.0.21-1.el7 被 mysql-community-server-8.0.21-1.el7.x86_64 需要
net-tools 被 mysql-community-server-8.0.21-1.el7.x86_64 需要
于是干脆下了mysql-8.0.21-1.el7.x86_64.rpm-bundle.tar包。
gwet https://......../ mysql-8.0.21-1.el7.x86_64.rpm-bundle.tar #自己去页面上找地址
tar -xvf mysql-8.0.21-1.el7.x86_64.rpm-bundle.tar
yum -y install net-tools mariadb-libs
rpm -ivh mysql-community-common-8.0.21-1.el7.x86_64.rpm
rpm -ivh mysql-community-libs-8.0.21-1.el7.x86_64.rpm
rpm -ivh mysql-community-client-8.0.21-1.el7.x86_64.rpm
rpm -ivh mysql-community-server-8.0.21-1.el7.x86_64.rpm
顺序不能错，有依赖关系。
启动服务：
systemctl start mysqld.service
systemctl enable mysqld.service
查看MySQL初始密码，每次安装都会不一样，注意使用自己机器上的：
grep 'password' /var/log/mysqld.log
2020-07-16T03:01:40.135985Z 6 [Note] [MY-010454] [Server] A temporary password is generated for root@localhost: _hN6j8t_pWaO
用初始密码进入MySQL
mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 8.0.21 MySQL Community Server - GPL
Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
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>
成功进入，修改密码：
mysql> alter user 'root'@'%' idenfified by 'wenfei@fly'; #报错，初始root用户在localhost下面，没有root@%用户。
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'idenfified by 'wenfei@fly'' at line 1
mysql> alter user 'root'@'localhost' identified by 'WenFei@123'; #先修改一次root@localhost用户，默认在本机登录
Query OK, 0 rows affected (0.01 sec)
user mysql;
create user 'root'@'%' identified by 'WenFei@123'; #创建root@%用户，方便其它IP登录访问数据库
#update user set host ='%' where user=‘root'; #也可以直接替换root@localhost为root@%用户
MySQL 8.0版本开始，密码默认使用的插件是caching_sha2_password，规则是大写、小写、字符、数字、至少8位，这些条件必须满足。如果要使用以前的mysql_native_password
ALTER USER `root`@`%` IDENTIFIED WITH mysql_native_password BY '123';
给root@%用户授权最大权限
grant all on *.* to root@'%';
好了，这时候可以用Navicat之类的工具连接了，如果不能连接请检查防火墙设置。
