CentOS 7.4 安裝 MySQL 5.7 及常見問題

確定系統版本

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

安裝方式

1. yum 安裝
2. 編譯安裝(以后有時間介紹，不同的系統不同的版本，編譯安裝會有各種不同的問題)

yum 安裝方式介紹

CentOS 7 默認安裝了mariadb數據庫，但是我們要使用MySQL

• 進入本機的源文件目錄
  • cd /usr/local/src/
• 下載MySQL的repo源
  • wget http://repo.mysql.com/mysql57-community-release-el7-8.noarch.rpm
• 安裝MySQL源
  • rpm -ivh mysql57-community-release-el7-8.noarch.rpm
• 使用yum安裝mysql-server(這個過程可能要30分鍾左右)
  • yum -y install mysql-server
• 安裝完成

總下載量：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

已安裝:
  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
  
作為依賴被安裝:
  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
  
作為依賴被升級:
  postfix.x86_64 2:2.10.1-7.el7
  
替代:
  mariadb-libs.x86_64 1:5.5.56-2.el7
  
完畢！

數據庫配置

• 啟動MySQL：systemctl start mysqld.service
• 查看MySQL狀態：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

• 查找數據庫root用戶的 臨時密碼：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

• 使用臨時密碼進入數據庫：mysql -uroot -p
• 如果不修改密碼，會有如下報錯

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

• 修改密碼，如果密碼太簡單，會有如下報錯

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

• 調整密碼后：

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

• 配置訪問權限

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

• 刷新權限(重要 ！！！)

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

• Done ！！！

MySQL 操作命令

• 啟動: systemctl start mysqld.service
• 重啟: systemctl restart mysqld.service
• 停止: systemctl stop mysqld.service
• 狀態: systemctl status mysqld.service
• 設置MySQL開機啟動: systemctl enable mysqld.service
• 停止MySQL開機啟動: systemctl disable mysqld.service

常見問題

• MySQL開啟外網訪問權限后還是無法訪問
  如果是阿里雲服務器，找到對應實例的安全組 > 配置規則 > 添加安全組規則：如下圖
  

• No more mirrors to try.
  安裝過程如果出現如下報錯，重新執行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"
正在嘗試其它鏡像。

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

• 問題：MySQL server has gone away
  在執行大文件的時候可能會報如上錯誤, 是因為MySQL限制了server接受的數據包的大小
  查看當前的大小配置：
  show VARIABLES like '%max_allowed_packet%';
  • 第一種方式：
    • 修改my.cnf(查找文件：mysql --help | grep my.cnf)
    • 添加：max_allowed_packet = 100M
  • 第二種方式(臨時解決方案, 數據庫重啟之后會失效)：
    • 首先命令行進入MySQL數據庫
    • 執行：set global max_allowed_packet=100*1024*1024;