阿里云上安装mysql_阿里云服务器上装的mysql执行mysql -u root -p没反应

1、下载Mysql的Yum仓库
        https://dev.mysql.com/downloads/repo/yum/

 2、将第一步下载的文件拖进服务器，进行安装：

     yum localinstall mysql80-community-release-el7-3.noarch.rpm

3、检测源是否安装成功

     yum repolist enabled | grep "mysql.-community."

4、选择版本

    vi /etc/yum.repos.d/mysql-community.repo

5、安装

    yum install mysql-community-server

6、启动mysql

    systemctl start mysqld

如果启动报如下错误错，则需要删除/var/lib目录下的mysql目录，是因为目标路径已经存在/var/lib/mysql /，导致无法初始化，删除完再次重启就行：

● mysqld.service - MySQL Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Sat 2020-12-12 16:53:16 CST; 1min 48s ago
     Docs: man:mysqld(8)
           http://dev.mysql.com/doc/refman/en/using-systemd.html
  Process: 18399 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS (code=exited, status=1/FAILURE)
  Process: 18373 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
 Main PID: 18399 (code=exited, status=1/FAILURE)
   Status: "Server startup in progress"
    Error: 2 (No such file or directory)

Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z mysqld[18399]: 2020-12-12T08:53:16.153655Z 0 [Warning] [MY-011070] [Server] 'Disabling symbolic links using --skip-symbolic-links (or e...re release.
Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z mysqld[18399]: 2020-12-12T08:53:16.155254Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.0.22) starting as process 18399
Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z mysqld[18399]: 2020-12-12T08:53:16.167524Z 1 [ERROR] [MY-011011] [Server] Failed to find valid data directory.
Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z mysqld[18399]: 2020-12-12T08:53:16.167640Z 0 [ERROR] [MY-010020] [Server] Data Dictionary initialization failed.
Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z mysqld[18399]: 2020-12-12T08:53:16.167694Z 0 [ERROR] [MY-010119] [Server] Aborting
Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z mysqld[18399]: 2020-12-12T08:53:16.168284Z 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 8.0.22)  MySQL C...rver - GPL.
Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z systemd[1]: mysqld.service: main process exited, code=exited, status=1/FAILURE
Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z systemd[1]: Failed to start MySQL Server.
Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z systemd[1]: Unit mysqld.service entered failed state.
Dec 12 16:53:16 iZ2zebcdfzd6516iqs3di2Z systemd[1]: mysqld.service failed.
Hint: Some lines were ellipsized, use -l to show in full.

7、设置开机自启动

     systemctl enable mysqld

    systemctl daemon-reload

 8、设置mysql密码：

    网上说的在/var/log/mysqld.log、/var/log/mysql.log中有密码，但进去后里面啥都没有。

   所以通过修改mysql配置文件，让他跳过密码使用root进入数据库

     ①找到/etc/my.cnf，编辑：vim /etc/my.cnf

     ②在[mysqld]标签下或者文件最下面添加一句skip-grant-tables

     ③esc退出编辑，然后输入 :wq保存退出 ，然后重启服务器 service mysqld restart 让修改生效

    ④mysql -u root 就可以直接进入数据库了。

    ⑤然后是修改密码，最好设置密码复杂点，建议：大写字母+小写字母+符号。否则后面mysql会报错让你改到符合mysql的安全策略，或者也可以修改mysql安全策略

          mysql> USE mysql;             

          可用命令查看 validate_password 密码验证插件是否安装：  mysql> SHOW VARIABLES LIKE 'validate_password%';

         MySQL 8.0 调整密码验证规则：

          mysql> set global validate_password.policy=0;

          mysql> set global validate_password.length=1;

       方案一：限制本地登录

                  ALTER USER 'root'@'localhost' IDENTIFIED BY '新密码';
                  flush privileges;

      方案二：可以任意IP与第三方客户端登录

ALTER USER 'root'@'localhost' IDENTIFIED BY '密码' PASSWORD EXPIRE NEVER;    #修改root的密码与加密方式
use mysql;   #切换到mysql库
update user set host='%' where user = 'root';   #更改可以登录的IP为任意IP
flush privileges;    #刷新权限
ALTER USER 'root'@'%' IDENTIFIED WITH mysql_native_password BY '密码'; #再次更改root用户密码，使其可以在任意IP访问
flush privileges;    #刷新权限

                mysql> quit

   ⑥改完密码，再将配置文件改回来，就把添加的那句删掉就好了，然后再次重启服务器service mysqld restart

   ⑦然后就可以使用 mysql -uroot -p输入你的新密码进入啦

问题总结： 通过查看 MySQL5.7 和 MySQL8.0 密码验证插件对比，可知两个版本中，变量名不一样。（*_password_policy 和 *_password.policy ）。