MYSQL will not start
Errcode: 13 means Access denied.  Assuming MySQL is trying to create a file in /tmp, which is 777 I guess this is incorrect configuration of either selinux or apparmor (on Debian systems).

Try to disable selinux

    echo 0 &gt;/selinux/enforce


If it doesn't help, stop apparmor (if you run Debian or Ubuntu)

    # /etc/init.d/apparmor stop
    # /etc/init.d/apparmor teardown