安装Mysql

运行以下命令更新YUM源。

rpm -Uvh  http://dev.mysql.com/get/mysql57-community-release-el7-9.noarch.rpm

运行以下命令安装MySQL。
说明如果您使用的操作系统内核版本为el8，可能会提示报错信息No match for argument。您需要先运行命令yum module disable mysql禁用默认的mysql模块，再安装MySQL。

yum -y install mysql-community-server

运行以下命令查看MySQL版本号。

mysql -V

返回结果如下所示，表示MySQL安装成功。

mysql  Ver 14.14 Distrib 5.7.28, for Linux (x86_64) using  EditLine wrapper

运行以下命令启动MySQL。

systemctl start mysqld

运行以下命令设置开机启动MySQL。

systemctl enable mysqld
systemctl daemon-reload

配置mysql

运行以下命令查看/var/log/mysqld.log文件，获取并记录root用户的初始密码。

grep 'temporary password' /var/log/mysqld.log

返回结果如下：

2016-12-13T14:57:47.535748Z 1 [Note] A temporary password is generated for root@localhost: p0/G28g>lsHD

说明下一步重置root用户密码时，会使用该初始密码。

运行以下命令配置MySQL的安全性。

mysql_secure_installation

安全性的配置包含以下五个方面：

1. 重置root账号密码，必须满足密码复杂度

Enter password for user root: #输入上一步获取的root用户初始密码
The 'validate_password' plugin is installed on the server.
The subsequent steps will run with the existing configuration of the plugin.
Using existing password for root.
Estimated strength of the password: 100 
Change the password for root ? (Press y|Y for Yes, any other key for No) : Y #是否更改root用户密码，输入Y
New password: #输入新密码，长度为8至30个字符，必须同时包含大小写英文字母、数字和特殊符号。特殊符号可以是()` ~!@#$%^&*-+=|{}[]:;‘<>,.?/
Re-enter new password: #再次输入新密码
Estimated strength of the password: 100 
Do you wish to continue with the password provided?(Press y|Y for Yes, any other key for No) : Y

输入Y删除匿名用户账号。

By default, a MySQL installation has an anonymous user, allowing anyone to log into MySQL without having to have a user account created for them. This is intended only for testing, and to make the installation go a bit smoother. You should remove them before moving into a production environment.
Remove anonymous users? (Press y|Y for Yes, any other key for No) : Y  #是否删除匿名用户，输入Y
Success.

输入Y禁止root账号远程登录。

Disallow root login remotely? (Press y|Y for Yes, any other key for No) : Y #禁止root远程登录，输入Y
Success.

输入Y删除test库以及对test库的访问权限。

Remove test database and access to it? (Press y|Y for Yes, any other key for No) : Y #是否删除test库和对它的访问权限，输入Y
- Dropping test database...
Success.

输入Y重新加载授权表。

Reload privilege tables now? (Press y|Y for Yes, any other key for No) : Y #是否重新加载授权表，输入Y
Success.
All done!

修改密码复杂度

mysql> show variables like '%validate_password%';

默认的情况下，密码策略是这样的, 默认8位长度并且要大小写。

+--------------------------------------+--------+
| Variable_name                        | Value  |
+--------------------------------------+--------+
| validate_password_check_user_name    | OFF    |
| validate_password_dictionary_file    |        |
| validate_password_length             | 8      |
| validate_password_mixed_case_count   | 1      |
| validate_password_number_count       | 1      |
| validate_password_policy             | MEDIUM |
| validate_password_special_char_count | 1      |
+--------------------------------------+--------+
7 rows in set (0.00 sec)

mysql> set global validate_password_policy=0; # 关闭密码复杂性策略

mysql> set global validate_password_length=1; # 设置密码复杂性要求密码最低长度为1

再次查看

mysql>  show variables like '%validate_password%' 
    -> ;
+--------------------------------------+-------+
| Variable_name                        | Value |
+--------------------------------------+-------+
| validate_password_check_user_name    | OFF   |
| validate_password_dictionary_file    |       |
| validate_password_length             | 4     |
| validate_password_mixed_case_count   | 1     |
| validate_password_number_count       | 1     |
| validate_password_policy             | LOW   |
| validate_password_special_char_count | 1     |
+--------------------------------------+-------+
7 rows in set (0.00 sec)