Mysql server ошибка установки

Aborting downgrade from (at least) 10.1 to 5.5. If are sure you want to downgrade to 5.5, remove the file /var/lib/mysql/debian-*.flag and
try installing again.

Собственно, вроде бы всё сказано. Пакетный менеджер обнаружил останки ранее стоявшей версии mysql (вероятно, форка, mariadb судя по номеру версии), при том численно более новой версии. Понижение версии может быть небезопасной операцией и может сломать имеющуюся базу, поэтому пакет отказывается ставиться и требует ручного вмешательства.

Поэтому сначала необходимо выяснить:

• а не запущена ли уже mariadb? Они будут конфликтовать в дефолтной установке.
• что там была за база данных и не нужна ли она больше

Если база не нужна — то сделайте бекап /var/lib/mysql и /etc/mysql — пригодятся, если вдруг выяснится, что да, база была нужна. Затем посмотрите в dpkg -l, скорей всего есть куски пакетов от mysql или mariadb не удалённые. Эти пакеты можно удалить через apt-get purge имя_пакета. После этого стоит удалить целиком /var/lib/mysql, если что-то ещё останется. Затем ставить снова mysql.

Если же вы понимаете что делаете и знаете что делать при проблемах (очевидно это не так) — удалите указанные файлы и повторите попытку установки.

Alternative solution: Use an administrator command prompt to run the MySQL installer on Windows 10. Details:

(Note: if you have any problems in the following steps, you can try to restart your computer. Then restart the steps.)

1. Right-click the Start/Windows icon in the bottom-left corner of Windows.
2. Click: Windows PowerShell (Admin).
3. A window asks: Do you want to allow this app to make changes to your device? Click: Yes.
4. Change to the directory with the MySQL installer. For example, if you downloaded the MySQL installer, type something like:

cd C:Usersmy_usernameDownloads

(Note: To save some typing, you can type a few characters, and then press the tab key, to make Windows show you various auto-completion options.)

1. Run the MySQL installer. Type something like the following command—make sure to include the period and backslash at the beginning—and press Enter.

.mysql-installer-community-8.0.11.0.msi

Note: The idea of using an administrator command prompt came from John Geffe, in the link below, which was cited in the answer written by the original poster (user8425592):

https://bugs.mysql.com/bug.php?id=82004

Bug #82004 MySQL Installer freezes during «Please wait while Windows configures…» phase

[6 Feb 3:58] John Geffe

To get past this problem I had to run the .msi installer from an the
Administrator command prompt. Hopefully this helps someone in the
future.

[19 Apr 18:14] Jim McCauley

John Geffe: Thanks! Your note on installing as an administrator seems
to have taken care of the problem.

Alternative solution: Use an administrator command prompt to run the MySQL installer on Windows 10. Details:

(Note: if you have any problems in the following steps, you can try to restart your computer. Then restart the steps.)

1. Right-click the Start/Windows icon in the bottom-left corner of Windows.
2. Click: Windows PowerShell (Admin).
3. A window asks: Do you want to allow this app to make changes to your device? Click: Yes.
4. Change to the directory with the MySQL installer. For example, if you downloaded the MySQL installer, type something like:

cd C:Usersmy_usernameDownloads

(Note: To save some typing, you can type a few characters, and then press the tab key, to make Windows show you various auto-completion options.)

1. Run the MySQL installer. Type something like the following command—make sure to include the period and backslash at the beginning—and press Enter.

.mysql-installer-community-8.0.11.0.msi

Note: The idea of using an administrator command prompt came from John Geffe, in the link below, which was cited in the answer written by the original poster (user8425592):

https://bugs.mysql.com/bug.php?id=82004

Bug #82004 MySQL Installer freezes during «Please wait while Windows configures…» phase

[6 Feb 3:58] John Geffe

To get past this problem I had to run the .msi installer from an the
Administrator command prompt. Hopefully this helps someone in the
future.

[19 Apr 18:14] Jim McCauley

John Geffe: Thanks! Your note on installing as an administrator seems
to have taken care of the problem.

This answer is also in answer to 16.04 upgrade broke mysql-server but which I cannot answer as the admin locked it to 10 reputation.

The error in APT occurs during the upgrade of Ubuntu to 16.04 (xenial) and Mysql from 5.5 to 5.7. Due to some packaging issues the APT upgrade ends in limbo because the post installation script of Mysql-server-5.7 fails to complete.

To solve the problem, try these steps:

1. apt purge mysql-server and apt autoremove to clean all traces of the old MYSQL. The database data will not be destroyed.
2. Remove everything from /etc/mysql directory.
3. Verify there is no old Mysql packages left installed: dpkg -l | grep mysql
4. apt install mysql-server to install

If these steps end in the same incomplete install, try the next step:

1. Tail -n 20 /var/log/mysql/error.log
2. The errors could be
   a. bad password for debian-sys-maint
   b. no memory for Innodb

Solve 2a: You need to upgrade the Mysql system tables from 5.5 to 5.7

Edit my.cnf to include under ‘[mysqld]’ the line «skip-grant-tables», service mysql start, and mysql_upgrade --force -u root -p

Solve 2b: You are short of memory for Mysql Innodb pool (are you on a micro-size server?)

Edit my.cnf to include under ‘[mysqld]’ the line
innodb_buffer_pool_size = 20M

the default innodb pool is 128M, that is tight in a 512M VM

To clear the APT error, do the post install again

dpkg --configure -a