package mysql-server-5.6 (not installed) failed to install/upgrade: le sous-processus nouveau script pre-installation a retourné une erreur de sortie d'état 1

[Jean Claveau]

The installation mysql server as dependency of build-deps of php-dev removed mariadb and didn't work.

ProblemType: Package
DistroRelease: Ubuntu 15.04
Package: mysql-server-5.6 (not installed)
ProcVersionSignature: Ubuntu 3.19.0-28.30-generic 3.19.8-ckt5
Uname: Linux 3.19.0-28-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.17.2-0ubuntu1.5
Architecture: amd64
Date: Mon Sep 28 12:38:04 2015
DuplicateSignature: package:mysql-server-5.6:(not installed):le sous-processus nouveau script pre-installation a retourné une erreur de sortie d'état 1
ErrorMessage: le sous-processus nouveau script pre-installation a retourné une erreur de sortie d'état 1
InstallationDate: Installed on 2015-07-20 (69 days ago)
InstallationMedia: Xubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422.1)
RelatedPackageVersions:
 dpkg 1.17.25ubuntu1
 apt 1.0.9.7ubuntu4.1
SourcePackage: mysql-5.6
Title: package mysql-server-5.6 (not installed) failed to install/upgrade: le sous-processus nouveau script pre-installation a retourné une erreur de sortie d'état 1
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.apparmor.d.usr.sbin.mysqld: 2015-07-11T20:43:37
mtime.conffile..etc.init.d.mysql: 2015-08-27T14:45:46.163455
mtime.conffile..etc.logrotate.d.mysql.server: 2015-07-11T20:43:48
mtime.conffile..etc.mysql.debian.start: 2015-02-17T19:24:15

[Robie Basak (racb)]

Thank you for your report.

Automatic migration from MariaDB 10.0 to MySQL 5.6 is currently not supported, so sorry that this isn't something that we can fix right now. You will need to fix your database manually.

[Jean Claveau (jean-claveau-g)]

Actually I found the way to fix it :
+ I had to remove whatever (sorry i don't remember) lock file in /var/...
+ force apt-get install
+ Launch mysql in safe mode
+ remove the plugins defined in the user table
+ restart mysql

The last steps are here :
 https://zhxq.io/how-to-solve-mariadb-plugin-unix_socket-is-not-loaded-problem-after-upgrade-to-ubuntu-15-04/