Tjyylli

After my VM server has fully crashed,
and I do not know why,
MariaDB on this Debian cannot be launched again.
Content of error.log with log files:

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: innodb_empty_free_list_algorithm has been changed to legacy because of small buffer pool size. In order to use backoff, increase buffer pool at least up to 20MB.



2019-04-15  0:40:43 139787712552320 [Note] InnoDB: Using mutexes to ref count buffer pool pages

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: The InnoDB memory heap is disabled

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: Compressed tables use zlib 1.2.8

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: Using Linux native AIO

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: Using SSE crc32 instructions

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: Initializing buffer pool, size = 128.0M

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: Completed initialization of buffer pool

2019-04-15  0:40:43 139787712552320 [Note] InnoDB: Highest supported file format is Barracuda.

InnoDB: No valid checkpoint found.

InnoDB: A downgrade from MariaDB 10.2.2 or later is not supported.

InnoDB: If this error appears when you are creating an InnoDB database,

InnoDB: the problem may be that during an earlier attempt you managed

InnoDB: to create the InnoDB data files, but log file creation failed.

InnoDB: If that is the case, please refer to

InnoDB: http://dev.mysql.com/doc/refman/5.6/en/error-creating-innodb.html

2019-04-15  0:40:43 139787712552320 [ERROR] Plugin 'InnoDB' init function returned error.

2019-04-15  0:40:43 139787712552320 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.

2019-04-15  0:40:43 139787712552320 [Note] Plugin 'FEEDBACK' is disabled.

2019-04-15  0:40:43 139787712552320 [ERROR] Unknown/unsupported storage engine: InnoDB

2019-04-15  0:40:43 139787712552320 [ERROR] Aborting

I doubt the ibdata1, ib_logfile0 and ib_logfile1 are corrupted
because I found another thread
where someone wanted to transfer their databases from one server to another
and the solution was properly shutdown MySQL on the server
before transfering the files.

If I remove the log files following other threads
which claim that MySQL / InnoDB can restore them,
the server crashes too but InnoDB complains that I may have missed to copy the log files. See log here (log posted on GitHub, too long for StackExchange)

If I also remove ibdata1, the server starts
but I cannot access the databases
because "The table 'xyz' doesn't exist in engine".
This thread mentions that I may can restore my data
but I cannot simply follow the solution as I have to apply it to over 200 tables.

I am using mysqld Ver 10.1.37-MariaDB-0+deb9u1 for debian-linux-gnu on x86_64 (Debian 9.6)
and I have used the default configuration of MariaDB for Debian except following:

[mysqld]

innodb_large_prefix=ON

innodb_file_format=barracuda

innodb_file_per_table=ON

Is there a way to restore or repair the database data?

PS: Now the server will get a cron job using mysqldump every hour to prevent the issue that the newest dump is over 2 months old ...