Job for mysqld.service failed because the control process exited with error code. See “systemctl sta

1.启动mysql8

systemctl start mysqld.service

报错

Job for mysqld.service failed because the control process exited with error code. See “systemctl status mysqld.service” and “journalctl -xe” for details.

2.按照提示查看

systemctl status mysqld.service

● mysqld.service - MySQL Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Tue 2021-11-30 09:04:16 CST; 22s ago
     Docs: man:mysqld(8)
           http://dev.mysql.com/doc/refman/en/using-systemd.html
  Process: 4149 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS (code=exited, status=1/FAILURE)
  Process: 4125 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
 Main PID: 4149 (code=exited, status=1/FAILURE)
   Status: "Data Dictionary upgrade from MySQL 5.7 in progress"

3.自己其实也不怎么看得懂

继续百度一下，发现这篇回答
mysql8不能启动

4.按照提示，操作，就行

主要就是说：我们要删除mysql 下的内容，现在无法启动，大概就是里面的内容有冲突，执行：

rm -rf /var/lib/mysql/*

查了一下，var/lib/包下的数据，是系统正常运行时要改变的文件.
5.再次启动，执行成功

[root@hecs-x-large-2-linux-20211127100244 ~]# systemctl start mysqld.service
[root@hecs-x-large-2-linux-20211127100244 ~]# ps -ef | grep mysql
mysql     4248     1  3 09:10 ?        00:00:00 /usr/sbin/mysqld
root      4296  3952  0 09:10 pts/0    00:00:00 grep --color=auto mysql