转自：https://www.jianshu.com/p/85bc42af03e7
- CentOS8.x已安装MySQL8.0.17
- 系统为：CentOS8.0.1905
- 最终安装MySQL版本：5.7.29
一、卸载MySQL8
1、查看版本
mysql --version
2、查看安装的包
rpm -qa | grep mysql
3、卸载已安装MySQL8
rpm -qa | grep mysql | xargs rpm -e --nodeps
删除MySQL配置文件及其目录
rm -rf /etc/my.cnf /etc/my.cnf.d
二、离线安装指定版本的MySQL
1、安装必要的包
yum install libncurses*
2、官网下载tar包
官网地址：https://dev.mysql.com/downloads/mysql/
(Looking for the latest GA version?)
Select Version: 5.7.29
Select Operating System: Source Code
Select OS Version： Generic Linux(Architecture Independent)
或者使用以下命令下载
cd /usr/local/src
wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-5.7.29-el7-x86_64.tar.gz
将离线下载的tar上传至/usr/local/src目录下
3、创建安装账户
mkdir /usr/local/mysql
useradd -s /bin/false -d /usr/local/mysql mysql
4、安装过程
# 此过程有点长，耐心等待
tar -xvzf mysql-5.7.21-el7-x86_64.tar.gz -C /usr/local/mysql/
cd /usr/local/mysql/mysql-5.7.21-el7-x86_64/
mv * ../
cd ..
rmdir mysql-5.7.21-el7-x86_64/
mkdir data
chown -R mysql.mysql ../mysql
cd bin
./mysqld --user=mysql --basedir=/usr/local/mysql --datadir=/usr/local/mysql/data --initialize
安装完成后在最后会显示root密码
拷贝可执行配置文件
cd /usr/local/mysql
cp ../support-files/mysql.server /etc/init.d/mysqld
5、配置过程
MySQL配置文件/etc/my.cnf中内容如下：
[mysqld]
port = 3306
basedir = /usr/local/mysql
datadir=/usr/local/mysql/data
socket=/tmp/mysql.sock
pid-file=/usr/local/mysql/data/mysql.pid
log-error=/usr/local/mysql/data/error.log
character_set_server=utf8
user=mysql
max_connections=1500
symbolic-links=0
# 东八区时区，北京时区
default-time-zone = '+8:00'
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
# 导入包允许的大小设置
max_allowed_packet=1024M
# 忽略表名大小写;1表示忽略大小写,0表示解析大小写
lower_case_table_names=1
!includedir /etc/my.cnf.d
6、启动服务并登陆
常用命令
# 启动命令
service mysqld start 或者 /etc/init.d/mysqld start
# 停止命令
service mysqld stop 或者 /etc/init.d/mysqld stop
# 重启命令
service mysqld restart 或者 /etc/init.d/mysqld restart
登陆命令
./bin/mysql -u root -p'zisTBE)I8*/0'
7、修改密码并允许远程连接
mysql> set password=password('123456');
mysql> use mysql;
mysql> update user set host='%' where user='root';
mysql> flush privileges;
如果远程还连接不上，看下是否防火墙开启了？
8、添加环境变量
vim /etc/profile
# mysql
PATH=/usr/local/mysql/bin:$PATH
保存退出后，使用
source /etc/profile使其生效。
三、MySQL自启
# 查看MySQL是否自启
systemctl is-enabled mysqld
如下图，显示disabled，MySQL默认非自启
# 开启自启
systemctl enable mysqld
如下图
四、防火墙放行3306端口
如果你的防火墙已经关闭，可忽略此操作。
# 永久开放3306端口
firewall-cmd --permanent --zone=public --add-port=3306/tcp
# 重启防火墙
systemctl restart firewalld
# 检测设定是否生效
iptables -nL | grep 3306
五、其他问题
问题1：yum仓库无法更新问题
在使用yum repolist列出仓库中的包时，出现Error: Failed to synchronize cache for repo 'AppStream'
由于其原有的默认的源配置文件被我删除过，然后CentOS8换过阿里的源，在卸载MySQL8之后重新安装后出现上述问题；解决参照：CentOS8使用阿里源。
将原来文件中
$releasever替换为8.0.1905，将$basearch替换为x86_64，然后再使用yum clean all && yum makecache即可
正常的CentOS-Base.repo内容如下
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-8.0.1905 - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8.0.1905/BaseOS/x86_64/os/
http://mirrors.aliyuncs.com/centos/8.0.1905/BaseOS/x86_64/os/
http://mirrors.cloud.aliyuncs.com/centos/8.0.1905/BaseOS/x86_64/os/
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official
#additional packages that may be useful
[extras]
name=CentOS-8.0.1905 - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8.0.1905/extras/x86_64/os/
http://mirrors.aliyuncs.com/centos/8.0.1905/extras/x86_64/os/
http://mirrors.cloud.aliyuncs.com/centos/8.0.1905/extras/x86_64/os/
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-8.0.1905 - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8.0.1905/centosplus/x86_64/os/
http://mirrors.aliyuncs.com/centos/8.0.1905/centosplus/x86_64/os/
http://mirrors.cloud.aliyuncs.com/centos/8.0.1905/centosplus/x86_64/os/
gpgcheck=1
enabled=0
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official
[PowerTools]
name=CentOS-8.0.1905 - PowerTools - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8.0.1905/PowerTools/x86_64/os/
http://mirrors.aliyuncs.com/centos/8.0.1905/PowerTools/x86_64/os/
http://mirrors.cloud.aliyuncs.com/centos/8.0.1905/PowerTools/x86_64/os/
gpgcheck=1
enabled=0
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official
[AppStream]
name=CentOS-8.0.1905 - AppStream - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8.0.1905/AppStream/x86_64/os/
http://mirrors.aliyuncs.com/centos/8.0.1905/AppStream/x86_64/os/
http://mirrors.cloud.aliyuncs.com/centos/8.0.1905/AppStream/x86_64/os/
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official
作者：静美书斋
链接：https://www.jianshu.com/p/ee018b20a6e6
来源：
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本人遇到的问题:
tar -zxvf mysql-5.7.32-linux-glibc2.12-x86_64.tar.gz -C /usr/local/
ln -s mysql-5.7.32-linux-glibc2.12-x86_64/ mysql
./bin/mysqld --user=mysql --basedir=/usr/local/mysql --datadir=/usr/local/mysql/data --initialize
错误：
error while loading shared libraries: libncurses.so.5: cannot open shared object file: No such file or directory
解决办法:
ln -s /usr/lib64/libncurses.so.6.1 /usr/lib64/libncurses.so.5
错误：
error while loading shared libraries: libtinfo.so.5: cannot open shared object file: No such file or directory
解决办法：
ln -s /usr/lib64/libtinfo.so.6.1 /usr/lib64/libtinfo.so.5
alter user 'root'@'localhost' identified by 'bpm,.123';