安装mysql后无法打开守护进程，报错如下：
- MySQL 8.0 database server
Loaded: loaded (/usr/lib/systemd/system/; disabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Wed 2021-03-10 02:25:22 CST; 13s ago
Process: 37172 ExecStopPost=/usr/libexec/mysql-wait-stop (code=exited, status=0/SUCCESS)
Process: 37170 ExecStart=/usr/libexec/mysqld --basedir=/usr (code=exited, status=1/FAILURE)
Process: 37133 ExecStartPre=/usr/libexec/mysql-prepare-db-dir (code=exited, status=0/SUCCESS)
Process: 37108 ExecStartPre=/usr/libexec/mysql-check-socket (code=exited, status=0/SUCCESS)
Main PID: 37170 (code=exited, status=1/FAILURE)
Status: “Server startup in progress”
Error: 13 (Permission denied)
解决方法：
卸载所有相关包重新安装：
rpm -q -a | grep sql
rpm -e mysql-common-8.0.21-1.module_el8.2.0+493+63b41e36.x86_64 mysql-8.0.21-1.module_el8.2.0+493+63b41e36.x86_64 mysql-server-8.0.21-1.module_el8.2.0+493+63b41e36.x86_64 mysql-errmsg-8.0.21-1.module_el8.2.0+493+63b41e36.x86_64 mysql-devel-8.0.21-1.module_el8.2.0+493+63b41e36.x86_64 mysql-libs-8.0.21-1.module_el8.2.0+493+63b41e36.x86_64
yum install mysql
yum install mysql-server
systemctl start mysqld
systemctl status
安装办法：
rpm -qa | grep -i mysql
rpm -e 上一步查询到的已安装包
wget /archives/get/p/23/file/MySQL-server-5.5.54-1.linux2.6.x86_64.rpm
wget /archives/get/p/23/file/MySQL-client-5.5.54-1.linux2.6.x86_64.rpm
rpm -ivh 上面两个文件
网站/downloads/mysql/