前言 ：最近自己的服务器重装了系统，上面的软件都没了，重装了MySQL5.7，但是遇到了许多问题，要么就是下载的是MySQL8.0要么就是mysql-community-server下载失败，经过几个小时的google终于安装上了，并且能够在本机的navicat(sqlyog)能够访问到服务器上的数据库。于是写了这篇详细的文档，给以后的自己以及遇到相同问题的朋友一个好的参考方案。

1. 卸载MySQL

安装之前先把服务器上关于MySQL的资源全部卸载，防止遇到不知名的错误(此方法同样适用于想卸载MySQL的)

• 1.1 yum方式查询是否安装了MySQL

  yum list installed mysql*
  

  如果出现：

  Dependencies resolved.
  ===============================================================================================================================================================================================
   Package                                              Architecture                         Version                                       Repository                                       Size
  ===============================================================================================================================================================================================
  Installing:
   mysql-community-server                               x86_64                               5.7.29-1.el7                                  mysql57-community                               175 M
  Installing dependencies:
   mysql-community-client                               x86_64                               5.7.29-1.el7                                  mysql57-community                                26 M
   mysql-community-common                               x86_64                               5.7.29-1.el7                                  mysql57-community                               311 k
   mysql-community-libs                                 x86_64                               5.7.29-1.el7                                  mysql57-community                               2.5 M
  
  Transaction Summary
  

  说明有，需要卸载。

• 1.2 yum方式卸载（如果有，则执行这一步）

  1. yum remove mysql-community-server mysql-community-client mysql-community-common mysql-community-libs
  2. rm -rf /var/lib/mysql
  3. rm /etc/my.cnf 
  

• 1.3 rpm查看是否安装mysql

  rpm -qa | grep -i mysql  
  

  如果出现

  mysql-community-client-5.7.27-1.el6.x86_64
  mysql-community-common-5.7.29-1.el7.x86_64
  mysql-community-server-5.7.29-1.el7.x86_64
  mysql-community-libs-5.7.27-1.el6.x86_64
  

  则说明存在

• 1.4 rpm卸载MySQL

  rpm -e mysql-community-client-5.7.27-1.el6.x86_64
  rpm -e mysql-community-common-5.7.29-1.el7.x86_64
  rpm -emysql-community-server-5.7.29-1.el7.x86_64
  rpm -e mysql-community-libs-5.7.27-1.el6.x86_64
  cd /var/lib/  
  rm -rf mysql/
  

• 1.5 清除剩余资源文件:

  whereis mysql
  出现：mysql: /usr/bin/mysql /usr/lib64/mysql /usr/share/mysql /usr/share/man/man1/mysql.1.gz
  删除：rm -rf "上面的资源文件(如：/usr/bin/mysql)"
  

• 1.6 删除MySQL残留的配置文件

  rm –rf /usr/my.cnf
  rm -rf /root/.mysql_sercret
  

• 1.7 再次检查是否完全删除

  chkconfig --list | grep -i mysql
  chkconfig --del mysqld
  

  如果还有资源没有删除干净，重复以上方法

2. 安装MySQL

• 2.1 添加MySQL存储库

  • 禁用MySQL默认的AppStream存储库：

    sudo dnf remove @mysql
    sudo dnf module reset mysql && sudo dnf module disable mysql
    

  • centos8没有MySQL存储库，因此我们将使用centos 7存储库。创建一个新的存储库文件。

    sudo vim /etc/yum.repos.d/mysql-community.repo
    

  • 将以下数据插入上面的存储库中

    [mysql57-community]
    name=MySQL 5.7 Community Server
    baseurl=http://repo.mysql.com/yum/mysql-5.7-community/el/7/$basearch/
    enabled=1
    gpgcheck=0
    
    [mysql-connectors-community]
    name=MySQL Connectors Community
    baseurl=http://repo.mysql.com/yum/mysql-connectors-community/el/7/$basearch/
    enabled=1
    gpgcheck=0
    
    [mysql-tools-community]
    name=MySQL Tools Community
    baseurl=http://repo.mysql.com/yum/mysql-tools-community/el/7/$basearch/
    enabled=1
    gpgcheck=0
    

• 2.2 安装MySQL(这里我选择MySQL5.7)

  sudo dnf --enablerepo=mysql57-community install mysql-community-server
  

• 2.2.1 如果安装失败,使用以下方法进行安装

  • 先下载rpm包

  wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-community-common-5.7.27-1.el6.x86_64.rpm
  wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-community-libs-5.7.27-1.el6.x86_64.rpm
  wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-community-client-5.7.27-1.el6.x86_64.rpm
  wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-community-server-5.7.27-1.el6.x86_64.rpm
  

  • 再安装

  yum install -y mysql-community-common-5.7.27-1.el6.x86_64.rpm
  yum install -y mysql-community-libs-5.7.27-1.el6.x86_64.rpm
  yum install -y mysql-community-client-5.7.27-1.el6.x86_64.rpm
  yum install -y mysql-community-server-5.7.27-1.el6.x86_64.rpm 
  

• 2.3 下载完成后检查版本

 [root@aliyun-zuojun ~]# rpm -qi mysql-community-server 
 Name        : mysql-community-server
 Version     : 5.7.29
 Release     : 1.el7
 Architecture: x86_64
 Install Date: Sat 22 Feb 2020 11:04:07 AM CST
 Group       : Applications/Databases
 Size        : 801919839
 License     : Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved. Under GPLv2 license as shown in the Description field.
 Signature   : DSA/SHA1, Thu 19 Dec 2019 04:12:40 PM CST, Key ID 8c718d3b5072e1f5
 Source RPM  : mysql-community-5.7.29-1.el7.src.rpm
 Build Date  : Wed 18 Dec 2019 09:31:48 PM CST
 Build Host  : loki02.no.oracle.com
 Relocations : (not relocatable)
 Packager    : MySQL Release Engineering <mysql-build@oss.oracle.com>
 Vendor      : Oracle and/or its affiliates
 URL         : http://www.mysql.com/
 Summary     : A very fast and reliable SQL database server

出现以上信息说明安装成功

• 2.4 检查 mysql 源是否安装成功

  yum repolist enabled | grep "mysql.*-community.*"
  出现以下信息说明安装成功：
  mysql-connectors-community MySQL Connectors Community                       141
  mysql-tools-community      MySQL Tools Community                            105
  mysql57-community          MySQL 5.7 Community Server
  

• 2.5 启动MySQL

   systemctl start mysqld
  

• 2.6 查看启动状态

  systemctl status mysqld
  // 出现以下信息，则启动成功
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
     Active: active (running) since Sat 2020-02-22 11:14:47 CST; 2h 19min ago
       Docs: man:mysqld(8)
             http://dev.mysql.com/doc/refman/en/using-systemd.html
    Process: 21345 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
    Process: 21323 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
   Main PID: 21349 (mysqld)
      Tasks: 30 (limit: 11516)
     Memory: 209.1M
     CGroup: /system.slice/mysqld.service
             ?..21349 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
  

• 2.7 设置开机启动

  systemctl enable mysqld
  

• 2.8 刷新所有修改过的配置文件

  systemctl daemon-reload
  

• 2.9 获取安装mysql后生成的临时密码，用于登录

  grep 'temporary password' /var/log/mysqld.log
  # 如果出现如下列信息，密码为: BL=azx(1u;Br
  2020-02-22T03:05:17.741049Z 1 [Note] A temporary password is generated for root@localhost: BL=azx(1u;Br
  

• 2.10 登录MySQL

  mysql -uroot -p
  # 再输入上面查找得到的临时密码即可进入mysql
  

• 2.11 修改登录密码

  mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass4!（修改后的密码，注意必须包含大小写字母数字以及特殊字符并且长度不能少于8位,否则会报错）';
  或者通过：mysql> set password for 'root'@'localhost'=password('MyNewPass4!');
  或者通过：mysql> use mysql;
          mysql> update user set password=PASSWORD('MyNewPass5!') where user='root';
          mysql> flush privileges;
  

• 2.12 添加远程登录用户(即本机访问服务器上的MySQL)

  mysql> GRANT ALL PRIVILEGES ON *.* TO 'zhangsan（用户名）'@'%' IDENTIFIED BY 'Zhangsan2018!（密码）' WITH GRANT OPTION;
  # 或者直接将root权限修改为可以通过远程访问(但不推荐)
  mysql> use mysql;
  mysql> UPDATE user SET Host='%' WHERE User='root';
  mysql> flush privileges;
  

• 2.13 设置默认编码为utf-8（mysql安装后默认不支持中文）

  vim /etc/my.cnf
  # 进入文件后添加下面的配置即可
  [mysqld]
  character-set-server=utf8
  [client]
  default-character-set=utf8
  [mysql]
  default-character-set=utf8
  

• 2.14 重启MySQL服务并进入MySQL

  shell> systemctl restart mysqld
  shell> mysql -uroot -p
  mysql> show variables like 'character%';
  

  • 出现如下则说明编码修改完成

  +--------------------------+----------------------------+
  | Variable_name            | Value                      |
  +--------------------------+----------------------------+
  | character_set_client     | utf8                       |
  | character_set_connection | utf8                       |
  | character_set_database   | utf8                       |
  | character_set_filesystem | binary                     |
  | character_set_results    | utf8                       |
  | character_set_server     | utf8                       |
  | character_set_system     | utf8                       |
  | character_sets_dir       | /usr/share/mysql/charsets/ |
  +--------------------------+----------------------------+
  

  • 退出MySQL

  mysql> quit
  

• 使用本机电脑navicat/sqlyog等一系列客户端工具连接服务器上的mysql，用户名和密码为远程用户的用户名和密码，如果是将root权限修改为可以远程访问，就用root访问。

以上就是全部对mysql的安装与卸载的教程，希望对你有帮助。

可以参考mysql官网文档：https://dev.mysql.com/doc/refman/5.7/en/linux-installation-yum-repo.html