我在centos 7上安装了mysql 8
当我想启动 mysqld 服务时，它说：
Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details
当我运行 systemctl status mysqld.service 时，它说：
mysqld.service - MySQL Server
Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor
preset: disabled)
Active: failed (Result: exit-code) since Mon 2020-01-13 06:01:53 EST; 6min ago
Docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
Process: 5532 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS (code=exited, status=1/FAILURE)
Process: 5504 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
Main PID: 5532 (code=exited, status=1/FAILURE)
Status: "Data Dictionary upgrade from MySQL 5.7 …