1、配置YUM源

在MySQL官网中下载YUM源rpm安装包

# 下载mysql源安装包
shell> wget https://dev.mysql.com/get/mysql57-community-release-el7-8.noarch.rpm
# 安装mysql源
shell> yum localinstall mysql57-community-release-el7-8.noarch.rpm

检查mysql源是否安装成功

shell> yum repolist enabled | grep “mysql.-community.”

看到上图所示表示安装成功。

可以修改vim /etc/yum.repos.d/mysql-community.repo源，改变默认安装的mysql版本。比如要安装5.6版本，将5.7源的enabled=1改成enabled=0。然后再将5.6源的enabled=0改成enabled=1即可。改完之后的效果如下所示：

2、安装MySQL

shell> yum install mysql-community-server

3、启动MySQL服务

shell> systemctl start mysqld

查看MySQL的启动状态

shell> systemctl status mysqld

● mysqld.service - MySQL Server

Loaded: loaded (/usr/lib/systemd/system/mysqld.service; disabled; vendor preset: disabled)

Active: active (running) since 五 2016-06-24 04:37:37 CST; 35min ago

Main PID: 2888 (mysqld)

CGroup: /system.slice/mysqld.service

└─2888 /usr/sbin/mysqld –daemonize –pid-file=/var/run/mysqld/mysqld.pid

6月 24 04:37:36 localhost.localdomain systemd[1]: Starting MySQL Server…

6月 24 04:37:37 localhost.localdomain systemd[1]: Started MySQL Server.

4、开机启动

shell> systemctl enable mysqld

shell> systemctl daemon-reload

5、修改root本地登录密码

mysql安装完成之后，在/var/log/mysqld.log文件中给root生成了一个默认密码。通过下面的方式找到root默认密码，然后登录mysql进行修改：

shell> grep ‘temporary password’ /var/log/mysqld.log

shell> mysql -uroot -p （直接打Enter）

mysql> use mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> update user set authentication_string = PASSWORD('123456') where user = 'root';
Query OK, 4 rows affected (0.00 sec)
Rows matched: 4  Changed: 4  Warnings: 0

mysql>  alter user 'root'@'localhost' identified by '123456';
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 'identified by '123456'' at line 1
mysql> grant all privileges on *.* to 'root'@'%' identified by '123456' with grant option;
Query OK, 0 rows affected (0.01 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

通过msyql环境变量可以查看密码策略的相关信息：

mysql> show variables like ‘%password%’;

validate_password_policy：密码策略，默认为MEDIUM策略

validate_password_dictionary_file：密码策略文件，策略为STRONG才需要

validate_password_length：密码最少长度

validate_password_mixed_case_count：大小写字符长度，至少1个

validate_password_number_count ：数字至少1个

validate_password_special_char_count：特殊字符至少1个

上述参数是默认策略MEDIUM的密码检查规则。

共有以下几种密码策略：

策略 检查规则

0 or LOW Length

1 or MEDIUM Length; numeric, lowercase/uppercase, and special characters

2 or STRONG Length; numeric, lowercase/uppercase, and special characters; dictionary file

MySQL官网密码策略详细说明：https://dev.mysql.com/doc/refman/5.7/en/validate-password-options-variables.html#sysvar_validate_password_policy

修改密码策略

在/etc/my.cnf文件添加validate_password_policy配置，指定密码策略

# 选择0（LOW），1（MEDIUM），2（STRONG）其中一种，选择2需要提供密码字典文件

validate_password_policy=0

如果不需要密码策略，添加my.cnf文件中添加如下配置禁用即可：

validate_password = off

重新启动mysql服务使配置生效：

systemctl restart mysqld

6、添加远程登录用户

默认只允许root帐户在本地登录，如果要在其它机器上连接mysql，必须修改root允许远程连接，或者添加一个允许远程连接的帐户，为了安全起见，我添加一个新的帐户：