I had the same error when trying to switch mysql-client and mysql-server from 5.5 to 5.6 (to version 5.6.28-0ubuntu0.14.04.1) by doing aptitude install mysql-server-5.6.
I found this in /var/log/syslog: Feb 22 10:47:53 esxh mysqld_safe[5421]: 2016-02-22 10:47:53 5420 [Note] InnoDB: 5.6.28 started; log sequence number 1626423 Feb 22 10:47:53 esxh mysqld_safe[5421]: ERROR: 1062 Duplicate entry 'innodb' for key 'PRIMARY' Feb 22 10:47:53 esxh mysqld_safe[5421]: 2016-02-22 10:47:53 5420 [ERROR] Aborting After purging mysql-client* and mysql-server* the installation of mysql 5.6 was successful. -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to mysql-5.6 in Ubuntu. https://bugs.launchpad.net/bugs/1400592 Title: package mysql-server-5.6 5.6.19-0ubuntu0.14.04.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mysql-5.6/+bug/1400592/+subscriptions -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs