mysql - 如何在不登录mysql的情况下恢复默认的[mysql]系统数据库？

Question

好的，所以我很渴望空间，但是却愚蠢地忽略了在Ubuntu 16 VPS上删除我的mysql系统数据库。 sql服务器崩溃后，我重新启动了systemctl mysql start并获取并检查journalctl -xe错误，告诉我：

nopnotme systemd[1]: Failed to start MySQL Community Server.
-- Subject: Unit mysql.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit mysql.service has failed.
--
-- The result is failed.
Nov 28 20:19:43 nopnotme systemd[1]: mysql.service: Unit entered failed state.
Nov 28 20:19:43 nopnotme systemd[1]: mysql.service: Failed with result 'exit-code'.

然后我检查了/var/log/mysql/error.log：

2019-11-28T19:40:30.996439Z 0 [Note] InnoDB: Creating shared tablespace for temporary tables
2019-11-28T19:40:30.996491Z 0 [Note] InnoDB: Setting file './ibtmp1' size to 12 MB. Physically writing the file full; Please wait ...
2019-11-28T19:40:31.130146Z 0 [Note] InnoDB: File './ibtmp1' size is now 12 MB.
2019-11-28T19:40:31.134049Z 0 [Note] InnoDB: 96 redo rollback segment(s) found. 96 redo rollback segment(s) are active.
2019-11-28T19:40:31.134066Z 0 [Note] InnoDB: 32 non-redo rollback segment(s) are active.
2019-11-28T19:40:31.138841Z 0 [Note] InnoDB: Waiting for purge to start
2019-11-28T19:40:31.189158Z 0 [Note] InnoDB: 5.7.28 started; log sequence number 3940166
2019-11-28T19:40:31.197376Z 0 [Note] Plugin 'FEDERATED' is disabled.
mysqld: Table 'mysql.plugin' doesn't exist
2019-11-28T19:40:31.201952Z 0 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
2019-11-28T19:40:31.202171Z 0 [ERROR] unknown option '--install'
2019-11-28T19:40:31.202181Z 0 [ERROR] Aborting

2019-11-28T19:40:31.202192Z 0 [Note] Binlog end
2019-11-28T19:40:31.202237Z 0 [Note] Shutting down plugin 'ngram'

ect ..（更多插件）

2019-11-28T19:40:31.202439Z 0 [Note] Shutting down plugin 'InnoDB'
2019-11-28T19:40:31.202487Z 0 [Note] InnoDB: FTS optimize thread exiting.
2019-11-28T19:40:31.202602Z 0 [Note] InnoDB: Starting shutdown...
2019-11-28T19:40:31.202670Z 0 [Note] InnoDB: Loading buffer pool(s) from /var/lib/mysql/ib_buffer_pool
2019-11-28T19:40:31.230348Z 0 [Note] InnoDB: Buffer pool(s) load completed at 191128 19:40:31 (/var/lib/mysql/ib_buffer_pool was empty)

所以我假设我没有遇到内存错误：

2019-11-28T19:40:31.230375Z 0 [Note] InnoDB: Dumping buffer pool(s) to /var/lib/mysql/ib_buffer_pool
2019-11-28T19:40:31.272173Z 0 [Note] InnoDB: Buffer pool(s) dump completed at 191128 19:40:31
2019-11-28T19:40:33.019782Z 0 [Note] InnoDB: Shutdown completed; log sequence number 3942367
2019-11-28T19:40:33.022780Z 0 [Note] InnoDB: Removed temporary tablespace data file: "ibtmp1"
2019-11-28T19:40:33.022793Z 0 [Note] Shutting down plugin 'MEMORY'
2019-11-28T19:40:33.022802Z 0 [Note] Shutting down plugin 'MyISAM'
2019-11-28T19:40:33.022812Z 0 [Note] Shutting down plugin 'sha256_password'
2019-11-28T19:40:33.022816Z 0 [Note] Shutting down plugin 'mysql_native_password'
2019-11-28T19:40:33.022943Z 0 [Note] Shutting down plugin 'binlog'
2019-11-28T19:40:33.023350Z 0 [Note] mysqld: Shutdown complete

我认为问题的根源在于我删除了系统文件，现在我无法登录以运行 mysql_upgrade

有什么想法吗？

编辑1
另请注意，/ var / lib / mysql目录的权限为 mysql:mysql

编辑2
我已经看到了这个问题： How to recover/recreate mysql's default 'mysql' database。但是，我无法登录并出现 Got error: 2002: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) when trying to connect错误。

Answer 1

解决了问题（解决方法）
位于/var/lib/mysql/{DATABASE}的已保存数据库文件* .frm和* .idb文件。
然后，我使用this方法卸载了sql-server。
重新安装并确认mysql正在运行并具有[information_schema]和[mysql]默认数据库后；我跟随this使用mysqlfrm --diagnostic {.frm file}重新生成表结构，以生成sql查询。
然后取消链接空的DATASPACE，以允许我导入我的真实DATASPACE（* .idb）。在将数据文件移回目录chown -R "mysql:mysql" /var/lib/mysql/时，请确保更新文件许可权。
备份并运行！