//下载
[root@localhost ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm
//安装
[root@localhost ~]# yum -y install mysql57-community-release-el7-10.noarch.rpm

[mysql-connectors-community]
name=MySQL Connectors Community
baseurl=https://mirrors.tuna.tsinghua.edu.cn/mysql/yum/mysql-connectors-community-el7-$basearch/
enabled=1
gpgcheck=1
gpgkey=https://repo.mysql.com/RPM-GPG-KEY-mysql
[mysql-tools-community]

name=MySQL Tools Community

baseurl=https://mirrors.tuna.tsinghua.edu.cn/mysql/yum/mysql-tools-community-el7-$basearch/

enabled=1

gpgcheck=1

gpgkey=https://repo.mysql.com/RPM-GPG-KEY-mysql
[mysql-5.6-community]

name=MySQL 5.6 Community Server

baseurl=https://mirrors.tuna.tsinghua.edu.cn/mysql/yum/mysql-5.6-community-el7-$basearch/

enabled=0

gpgcheck=1

gpgkey=https://repo.mysql.com/RPM-GPG-KEY-mysql
[mysql-5.7-community]

name=MySQL 5.7 Community Server

baseurl=https://mirrors.tuna.tsinghua.edu.cn/mysql/yum/mysql-5.7-community-el7-$basearch/

enabled=1

gpgcheck=1

gpgkey=https://repo.mysql.com/RPM-GPG-KEY-mysql
[mysql-8.0-community]

name=MySQL 8.0 Community Server

baseurl=https://mirrors.tuna.tsinghua.edu.cn/mysql/yum/mysql-8.0-community-el7-$basearch/

enabled=0//默认安装最新版本，因为自己要安装5.7，所有把enabled=1改成enabled=0

gpgcheck=1

gpgkey=https://repo.mysql.com/RPM-GPG-KEY-mysql

 sudo yum install -y mysql-community-server

sudo service mysqld start

sudo service mysqld status

查看初始化密码：
sudo grep ‘temporary password‘ /var/log/mysqld.log

使用初始密码进行登录：
mysql -u root -p

初始化密码
ALTER USER ‘root‘@‘localhost‘ IDENTIFIED BY ‘初始化密码‘;

 SHOW VARIABLES LIKE ‘validate_password%‘; 

set global validate_password_policy=LOW; 

set global validate_password_length=6;

ALTER USER ‘root‘@‘localhost‘ IDENTIFIED BY ‘123456‘;

//这里设置登录密码和远程连接密码都是123456
GRANT ALL PRIVILEGES ON *.* TO ‘root‘@‘%‘ IDENTIFIED BY ‘123456‘ WITH GRANT OPTION;
//刷新权限
FLUSH PRIVILEGES;

systemctl enable mysqld

firewall-cmd --zone=public --add-port=3306/tcp --permanent
//重启防火墙
firewall-cmd --reload
//验证3306是否开放成功
firewall-cmd --zone=public --query-port=3306/tcp