mysql启动不了，显示error message = 'System schema directory does not exist.'.

#mysql启动不成功查看错误日志显示
2022-02-26T08:57:37.597100Z 0 [Warning] [MY-000081] [Server] option 'max_allowed_packet': unsigned value 107374182400 adjusted to 1073741824.
2022-02-26T08:57:37.597178Z 0 [Warning] [MY-010915] [Server] 'NO_ZERO_DATE', 'NO_ZERO_IN_DATE' and 'ERROR_FOR_DIVISION_BY_ZERO' sql modes should be used with strict mode. They will be merged with strict mode in a future release.
2022-02-26T08:57:37.597266Z 0 [System] [MY-010116] [Server] /www/server/mysql/bin/mysqld (mysqld 8.0.24) starting as process 11150
2022-02-26T08:57:37.634849Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
2022-02-26T08:57:37.881075Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
2022-02-26T08:57:37.882114Z 1 [ERROR] [MY-013178] [Server] Execution of server-side SQL statement 'CREATE SCHEMA mysql DEFAULT COLLATE utf8mb4_general_ci' failed with error code = 1049, error message = 'System schema directory does not exist.'.
2022-02-26T08:57:37.882402Z 0 [ERROR] [MY-010020] [Server] Data Dictionary initialization failed.
2022-02-26T08:57:37.882672Z 0 [ERROR] [MY-010119] [Server] Aborting
2022-02-26T08:57:38.403640Z 0 [System] [MY-010910] [Server] /www/server/mysql/bin/mysqld: Shutdown complete (mysqld 8.0.24) Source distribution.

解决了，是少了一个名字叫mysql的库，我自己在data目录下创建了一个mysql文件夹，设置好了权限，在里面创建了一个名字叫db.opt的文件，写了两行内容
default-character-set=utf8
default-collation=utf8_general_ci
然后就启动成功了！！！
总结一下吧：
碰到问题，一定要看错误日志，围绕着错误日志去解决就好了。
linux中所有的东西，都只是文件和文件夹

你应该是删除了系统文件才导致的吧，mysql8初始化后会在根目录生成一个data目录，里面记录你的操作，建的数据库等信息，另外数据库初始化完成后除了root用户，还有两个系统用户千万别删，另外系统数据库也不要随便删除，前面那两个最好不要做任何操作
information_schema
performance_schema
mysql
如果你有能力将之前删除的再补回来也是可以的，没有的话可以删除data文件夹，然后重新初始化mysql即可

系统文件不存在了，建议重新下载一个。
如果答案，您满意，请采纳意见，支持一下，谢谢！