So is this not a technical support forum?
This is a support forum for WordPress issues. You have a MySQL issue.
the mysql daemon process dies as soon as a WordPress page is loaded so it's absolutely WordPress related.
The process dies when you try to create the user in MySQL.
- Maybe you have a problem with the bind address in my.conf
- Or maybe if you just run the mysql_upgrade routine, that might be enough to solve your issue.
https://bugs.mysql.com/bug.php?id=68385
http://manpages.ubuntu.com/manpages/lucid/man1/mysql_upgrade.1.html
Search out references specific to the error, your version of Ubuntu, and MySQL. WordPress is not the problem in this case.