sudo apt-get -f install
Reading package lists... Done
Building dependency tree       
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.
2 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Setting up mysql-server-5.5 (5.5.41-0ubuntu0.12.04.1) ...
150417  9:35:27 [Warning] Using unique option prefix key_buffer instead of key_buffer_size is deprecated and will be removed in a future release. Please use the full name instead.
150417  9:35:27 [ERROR] Fatal error: Can't change to run as user 'mysql' ;  Please check that the user exists!

150417  9:35:27 [ERROR] Aborting

150417  9:35:27 [Note] /usr/sbin/mysqld: Shutdown complete

start: Job failed to start
invoke-rc.d: initscript mysql, action "start" failed.
dpkg: error processing mysql-server-5.5 (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of mysql-server:
 mysql-server depends on mysql-server-5.5; however:
  Package mysql-server-5.5 is not configured yet.
dpkg: error processing mysql-server (--configure):
 dependency problems - leaving unconfigured
No apport report written because the error message indicates its a followup error from a previous failure.
                          Errors were encountered while processing:
 mysql-server-5.5
 mysql-server
E: Sub-process /usr/bin/dpkg returned an error code (1)