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Fwd: database corrupted when switching from MySQL to MariaDB on Ubuntu 19.04

 

@Andrei all the error messages I found were included in my original email,
let me know how I can provide additional information if no one can
reproduce the problem.
I forgot to include maria-discuss@xxxxxxxxxxxxxxxxxxx, you can see my reply
below.

---------- Forwarded message ---------
From: bapt x <baptx.is@xxxxxxxxx>
Date: Wed, 16 Oct 2019 at 10:35
Subject: Re: [Maria-discuss] database corrupted when switching from MySQL
to MariaDB on Ubuntu 19.04
To: Gordan Bobic <gordan.bobic@xxxxxxxxx>


Thanks for the information. It looks like I did everything properly since I
was able to reproduce the problem several times with a clean install of
Ubuntu 19.04 on VirtualBox. I think if someone else tries the steps I
explained, he can reproduce the problem. Now it would be nice to know if
there is a way to recover the data. If MariaDB was able to corrupt the
data, there should be a way to reverse engineer the process and restore the
data. Maybe a developer that knows well MariaDB upgrade system has a
solution.

On Wed, 16 Oct 2019 at 10:23, Gordan Bobic <gordan.bobic@xxxxxxxxx> wrote:

> I don't know if it is recoverable but it sounds like you missed the step
> of always needing a full, clean shutdown between upgrades with
> innodb_fast_shutdown=0. Then you can delete ib_logfile*, and upgrade.
>
> On Wed, 16 Oct 2019, 09:19 bapt x, <baptx.is@xxxxxxxxx> wrote:
>
>> Hello,
>>
>> On Ubuntu 19.04, which uses packages mariadb-server 10.3.17 and
>> mysql-server 5.7.27, I noticed that if I wanted to switch from MySQL to
>> MariaDB, the database is corrupted and there is a complete data loss
>> even if I switch back to MySQL.
>> In the previous version of Ubuntu, switching from MySQL to MariaDB did
>> not manage to import data automatically (unlike Debian) but at least it
>> created a backup of the data in /var/lib/mysql-5.7/ folder which is not
>> done anymore.
>>
>> Here is the error message I saw during install when trying to use the
>> database corrupted by MariaDB and switching back to MySQL:
>> "MySQL has been frozen to prevent damage to your system. Please see
>> /etc/mysql/FROZEN for help."
>>
>> And in /var/log/mysql/error.log:
>> "[ERROR] InnoDB: Unsupported redo log format. The redo log was created
>> with MariaDB 10.3.17. Please follow the instructions athttp://dev.mysql.com/doc/refman/5.7/en/upgrading-downgrading.html";
>>
>> I was able to reproduce the issue with a clean installation of Ubuntu
>> 19.04 in VirtualBox.
>>
>> Do you know where the problem comes from and if it is possible to fix
>> the binary data from */var/lib/mysql/* to make it work with either MySQL
>> or MariaDB?
>> It looks like MariaDB tried to convert the data ("[ERROR] InnoDB:
>> Unsupported redo log format") but now it fails with both MySQL and MariaDB.
>> Is it possible to revert the changes done by MariaDB to make the data
>> work again with MySQL? (and then do a proper backup with mysqldump)
>>
>> Thanks.
>>
>> _______________________________________________
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>

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