CentOS 7.4 安装 MySQL 5.7 及常见问题

确定系统版本

命令：cat /etc/centos-release
输入：CentOS Linux release 7.4.1708 (Core)

安装方式

1. yum 安装
2. 编译安装(以后有时间介绍，不同的系统不同的版本，编译安装会有各种不同的问题)

yum 安装方式介绍

CentOS 7 默认安装了mariadb数据库，但是我们要使用MySQL

• 进入本机的源文件目录
  • cd /usr/local/src/
• 下载MySQL的repo源
  • wget http://repo.mysql.com/mysql57-community-release-el7-8.noarch.rpm
• 安装MySQL源
  • rpm -ivh mysql57-community-release-el7-8.noarch.rpm
• 使用yum安装mysql-server(这个过程可能要30分钟左右)
  • yum -y install mysql-server
• 安装完成

总下载量：208 M
Downloading packages:
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
(1/7): libaio-0.3.109-13.el7.x86_64.rpm                      |  24 kB  00:00:00
(2/7): mysql-community-common-5.7.29-1.el7.x86_64.rpm        | 311 kB  00:00:04
(3/7): mysql-community-libs-5.7.29-1.el7.x86_64.rpm          | 2.5 MB  00:01:39     
(4/7): mysql-community-libs-compat-5.7.29-1.el7.x86_64.rpm   | 1.3 MB  00:00:44     
(5/7): postfix-2.10.1-7.el7.x86_64.rpm                       | 2.4 MB  00:00:00     
(6/7): mysql-community-client-5.7.29-1.el7.x86_64.rpm        |  26 MB  00:09:19     
(7/7): mysql-community-server-5.7.29-1.el7.x86_64.rpm        | 175 MB  00:28:37

已安装:
  mysql-community-libs.x86_64 0:5.7.29-1.el7
  mysql-community-libs-compat.x86_64 0:5.7.29-1.el7
  mysql-community-server.x86_64 0:5.7.29-1.el7
  
作为依赖被安装:
  libaio.x86_64 0:0.3.109-13.el7
  mysql-community-client.x86_64 0:5.7.29-1.el7
  mysql-community-common.x86_64 0:5.7.29-1.el7
  
作为依赖被升级:
  postfix.x86_64 2:2.10.1-7.el7
  
替代:
  mariadb-libs.x86_64 1:5.5.56-2.el7
  
完毕！

数据库配置

• 启动MySQL：systemctl start mysqld.service
• 查看MySQL状态：systemctl status mysqld.service

● mysqld.service - MySQL Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: active (running) since 日 2020-03-29 01:28:50 CST; 16s ago

• 查找数据库root用户的 临时密码：grep "password" /var/log/mysqld.log

2020-03-28T17:28:47.341327Z 1 [Note] A temporary password is generated for root@localhost: :8#I;as5F/yw

• 使用临时密码进入数据库：mysql -uroot -p
• 如果不修改密码，会有如下报错

mysql> show databases;
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.

• 修改密码，如果密码太简单，会有如下报错

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY '123';
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements

• 调整密码后：

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'Limm123!!';
Query OK, 0 rows affected (0.00 sec)

• 配置访问权限

mysql> update mysql.user set host='%' where host='localhost';
Query OK, 3 rows affected (0.00 sec)
Rows matched: 3  Changed: 3  Warnings: 0

• 刷新权限(重要 ！！！)

mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

• Done ！！！

image

MySQL 操作命令

• 启动: systemctl start mysqld.service
• 重启: systemctl restart mysqld.service
• 停止: systemctl stop mysqld.service
• 状态: systemctl status mysqld.service
• 设置MySQL开机启动: systemctl enable mysqld.service
• 停止MySQL开机启动: systemctl disable mysqld.service

常见问题

• MySQL开启外网访问权限后还是无法访问
  如果是阿里云服务器，找到对应实例的安全组 > 配置规则 > 添加安全组规则：如下图

  
  image

• No more mirrors to try.
  安装过程如果出现如下报错，重新执行yum就好

mysql-community-common-5.7.29- FAILED                                          
http://repo.mysql.com/yum/mysql-5.7-community/el/7/x86_64/mysql-community-common-5.7.29-1.el7.x86_64.rpm: 
[Errno 14] curl#6 - "Could not resolve host: repo.mysql.com; Unknown error"
正在尝试其它镜像。

Error downloading packages:
  mysql-community-common-5.7.29-1.el7.x86_64: [Errno 256] No more mirrors to try.

• 问题：MySQL server has gone away
  在执行大文件的时候可能会报如上错误, 是因为MySQL限制了server接受的数据包的大小
  查看当前的大小配置：
  show VARIABLES like '%max_allowed_packet%';
  • 第一种方式：
    • 修改my.cnf(查找文件：mysql --help | grep my.cnf)
    • 添加：max_allowed_packet = 100M
  • 第二种方式(临时解决方案, 数据库重启之后会失效)：
    • 首先命令行进入MySQL数据库
    • 执行：set global max_allowed_packet=100*1024*1024;