1.检查是否安装mariadb
rpm -qa | grep mariadb
若有会显示
mariadb-libs-5.5.56-2.el7.x86_64
2.卸载mariadb
rpm -e --nodeps mariadb-libs-5.5.56-2.el7.x86_64
cd /etc
rm -rf my.cnf.rpmsave
3.清理原有的mysql数据库
查找安装的mysql软件包和依赖包：
rpm -qa | grep mysql
若原有mysql，会显示类似下列结果：
mysql80-community-release-el7-1.noarch
mysql-community-server-8.0.11-1.el7.x86_64
mysql-community-common-8.0.11-1.el7.x86_64
mysql-community-libs-8.0.11-1.el7.x86_64
mysql-community-client-8.0.11-1.el7.x86_64
使用以下命令依次删除上面的程序：
yum remove mysql-xxx-xxx
删除mysql的配置文件，卸载不会自动删除配置文件，首先使用命令查找出所有用的配置文件：
find / -name mysql
可能显示如下结果：
/etc/logrotate.d/mysql
/etc/selinux/targeted/active/modules/100/mysql
/etc/selinux/targeted/tmp/modules/100/mysql
/var/lib/mysql
/var/lib/mysql/mysql
/usr/bin/mysql
/usr/lib64/mysql
/usr/local/mysql
根据需求使用一下命令，依次删除配置文件
rm -rf /etc/logrotate.d/mysql
4.yum仓库下载mysql
yum localinstall https://repo.mysql.com//mysql80-community-release-el7-2.noarch.rpm
5.查看mysql yum仓库中的mysql版本
yum repolist all | grep mysql
6.yum安装mysql
yum install mysql-community-server
7.启动mysql服务
service mysqld start
systemctl start mysqld.service
8.检查mysql服务状态
service mysqld status
systemctl status mysqld.service
9.获取mysql初始登陆密码
cat /var/log/mysqld.log | grep password
grep 'temporary password' /var/log/mysqld.log
10.使用初始密码登陆
mysql -uroot -p
输入上面的密码
11.修改root登陆密码
use mysql;
alter user 'root'@'localhost' identified by '密码';
12.允许外网ip访问
mysql -uroot -p
use mysql;
update user set host = '%' where user = 'root';
quit;
systemctl restart mysqld.service
13.修改身份认证默认插件，允许客户端访问
mysql -uroot -p
alter user 'root'@'%' identified with mysql_native_password by '密码';
14.开放3306端口
firewall-cmd --zone=public --add-port=3306/tcp --permanent
firewall-cmd --reload
firewall-cmd --zone=public --query-port=3306/tcp
参考文章：
https://blog.csdn.net/managementandjava/article/details/80039650 yum安装
https://www.cnblogs.com/hujiapeng/p/9124298.html yum安装
https://blog.csdn.net/xufengzhu/article/details/81110982 启动服务
https://www.cnblogs.com/qianzf/p/7082484.html 服务查询
https://blog.csdn.net/qq_36999656/article/details/79840084 设置ip访问权限
http://www.bubuko.com/infodetail-2691539.html 设置客户端访问
https://blog.csdn.net/dufufd/article/details/82078564 防火墙
https://blog.csdn.net/ywd1992/article/details/80401630 防火墙
https://www.cnblogs.com/huizhipeng/p/10127333.html firewall开放端口
https://www.cnblogs.com/moxiaoan/p/5683743.html firewall关闭端口