1. 检测是否自带Mysql
rpm -qa | grep mysql
2. 若已安装，可卸载
rpm -e mysql-libs.x86_64??（已安装的包名） // 普通删除模式 rpm -e --nodeps mysql-libs.x86_64?? // 强力删除模式，如果使用上面命令删除时，提示有依赖的其它文件，则用该命令可以对其进行强力删除
3. 下载mysql57
yum install wget
wget https://repo.mysql.com//mysql57-community-release-el7-9.noarch.rpm
rpm -Uvh http://dev.mysql.com/get/mysql57-community-release-el7-9.noarch.rpm # *上两句有点问题，用这个* #
4. # *3*若成功，这步忽略# 使用rpm安装
rpm -ivh mysql57-community-release-el7-9.noarch.rpm
5. 安装mysql-community-server
yum -y install mysql-community-server
6. 初始化 MySQL、开机启动设置
mysqld --initialize
systemctl enable mysqld systemctl daemon-reload
7. 启动mysql服务
service mysqld start
8. 此时出现报错
Redirecting to /bin/systemctl start mysqld.service Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details.
查看mysql服务的启动日志
tail -f /var/log/mysqld.log
遇到一大堆问题
1）查看/var/run/mysqld/的属主和属组是root，mysql并不能在其中创建文件，后修改该目录的属主和属组
chown mysql.mysql /var/run/mysqld/
2）ibdata1等文件不能被写入，进入mysql安装目录，修改文件权限
chmod 777 /var/lib/mysql/ibdata1
3）Failed to create file(file: './auto.cnf', errno 13)，修改整个目录的权限
chmod -R 777 /var/lib/mysql/
以下未部分报错信息，做了很多操作无效，改了权限后不报错（暂时无视）
[ERROR] InnoDB: Cannot open datafile for read-only: './sys/sys_config.ibd' OS error: 81 [ERROR] Initialization of the server's UUID failed because it could not be read from the auto.cnf file. If this is a new server, the initialization failed because it was not possible to generate a new UUID.
9. 重启sql
service mysqld restart
10. 查看 MySQL 运行状态
service mysqld status 或systemctl status mysqld
● mysqld.service - MySQL Server
Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
Active: active (running) since Sat 2018-09-15 23:49:41 CST; 21min ago
Docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
Process: 32312 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
Process: 32294 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
Main PID: 32316 (mysqld)
CGroup: /system.slice/mysqld.service
└─32316 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
Sep 15 23:49:41 iZbp1iir8v4wm901e3gmz0Z systemd[1]: mysqld.service holdoff time over, s....
Sep 15 23:49:41 iZbp1iir8v4wm901e3gmz0Z systemd[1]: Starting MySQL Server...
Sep 15 23:49:41 iZbp1iir8v4wm901e3gmz0Z systemd[1]: Started MySQL Server.
Hint: Some lines were ellipsized, use -l to show in full.
11. 验证mysql安装
[root@iZbp1iir8v4wm901e3gmz0Z init.d]# mysqladmin --version mysqladmin Ver 8.42 Distrib 5.7.23, for Linux on x86_64
12. 创建用户名密码，只记用到的指令吧，一个个来....
1）因为修改时候报错，所以先修改配置文件vim /etc/my.cnf，文件末尾一行加上skip-grant-tables不需要密码登录，保存后重启mysql，执行service mysqld restart
2）用root账号进入mysql，指令：mysql -uroot -p，进入mysql界面，输入use mysql，使用select user,host from user; 查看是否有用户名为空的localhost用户，若有则删除：Delete FROM user Where User='' and Host='localhost';（我把除root以外的用户都删了），执行成功后刷新MySQL的系统权限相关表，以防止更改后拒绝访问，执行flush privileges;
3）修改root的密码：在mysql中输入指令update user set authentication_string=password('Jxxjxx68024787') where user='root'
4）将配置vim /etc/my.cnf中的不需要密码登录那一行注销，并重启mysql：service mysqld restart
5）此时进入mysql又出妖蛾子，输入啥都提示改密码，那特么只能改了啊，输入：alter user user() identified by "新密码";
问题参考：https://blog.csdn.net/muziljx/article/details/81541896
这里在想，既然又让改密码，是不是3）修改root的密码这一步可以省略？
6）由于上面这个报错，在配置vim /etc/my.cnf中加入一行，设置密码永不过期：default_password_lifetime=0
注意：若修改过mysql的用户名密码，wordpress配置需要修改相关内容，vim /var/www/html/wp-config.php
nginx下修改vim /usr/share/nginx/html/wp-config.php
13. 开启远程访问
修改配置文件vim /etc/my.cnf，新增一行（若已存在则修改地址）bind-address = 0.0.0.0
14. 新增用户，进入mysql中输入指令GRANT ALL PRIVILEGES ON *.* TO 'user'@'%' IDENTIFIED BY 'password' WITH GRANT OPTION;（user处填用户名，%表示所有的电脑都可以连接，也可以设置某个ip地址运行连接，password处填密码）。
