Oct 20 09:51:52 localhost.localdomain systemd[1]: Starting MySQL Server...
-- Subject: Unit mysqld.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit mysqld.service has begun starting up.
Oct 20 09:51:52 localhost.localdomain systemd[1]: mysqld.service: main process exited, code=exited, status=1/FAILURE
Oct 20 09:51:52 localhost.localdomain systemd[1]: Failed to start MySQL Server.
-- Subject: Unit mysqld.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit mysqld.service has failed.
-- 
-- The result is failed.
Oct 20 09:51:52 localhost.localdomain systemd[1]: Unit mysqld.service entered failed state.
Oct 20 09:51:52 localhost.localdomain systemd[1]: mysqld.service failed.
Oct 20 09:51:52 localhost.localdomain polkitd[691]: Unregistered Authentication Agent for unix-process:12812:15913826 (system bus name :1.100, object path /org/freedesktop/PolicyKit1/AuthenticationAgent, local

排错步骤：

1、systemctl status mysqld.service 没有具体失败原因

2、journalctl -xe

这里搜索了一下Unregistered Authentication Agent for unix-process:4804:62582...这个错误描述，没有找到有用的解决方案。

3、打开mysql的配置文件my.cnf, 找到错误日志路径，这里是

/var/log/mysqld.log

这里找到了直接的错误原因，binlog.index无权限，

解决方案：

chown mysql.mysql /var/lib/mysql/binlog.index

结束。