yum方式安裝Myql

環境
OS：CentOS7.6
Mysql：Mysql5.7

1. 獲取更新包
   Mysql官網:https://dev.mysql.com/
   到http://dev.mysql.com/downloads/repo/yum/ 去下載rpm包更新一下。

   #下載mysql源安裝包
   wget http://dev.mysql.com/get/mysql57-community-release-el7-8.noarch.rpm
   #安裝mysql源
   yum localinstall mysql57-community-release-el7-8.noarch.rpm
   #檢測源是否安裝成功
   yum repolist enabled | grep "mysql.*-community.*"

2. 安裝
   修改配置yum 安裝mysql的版本，這裏安裝MySQL5.7版本，修改“enabled=1”。
   vim /etc/yum.repos.d/mysql-community.repo

   #Enable to use MySQL 5.6
   [mysql56-community]
   name=MySQL 5.6 Community Server
   baseurl=http://repo.mysql.com/yum/mysql-5.6-community/el/7/$basearch/
   enabled=0
   gpgcheck=1
   gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql
   [mysql57-community]
   name=MySQL 5.7 Community Server
   baseurl=http://repo.mysql.com/yum/mysql-5.7-community/el/7/$basearch/
   enabled=1
   gpgcheck=1
   gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql

   yum安裝

   yum install mysql-community-server

   systemctl start mysqld //啓動mysql服務
   systemctl status mysqld
   systemctl enable mysqld
   systemctl daemon-reload //重載服務

3. 配置
   mysql5.7安裝時會產生一個默認密碼，查看此密碼的文件一般存在於/var/log/mysqld.log上。
   grep 'temporary password' /var/log/mysqld.log
   
   登錄mysql
   mysql -uroot -p
   
   可看到mysql5.7版本默認登錄後要求修改密碼，採用了密碼機制，默認爲medium，要求密碼有大寫字母及特殊字符。
   修改密碼：

   mysql> set password for 'root'@'localhost'=password('xxxxxxxx');

   查看密碼策略：

   mysql> show variables like '%password%'

   
   0 => LOW，1 => MEDIUM，2 => STRONG
   命令行修改：
   set global validate_password_policy=0; //設置密碼策略等級
   set global validate_password_length=6； //設置密碼最小長度
   重啓mysql服務
   systemctl restart mysqld