"SQL Error: 13: Can't create/write to file" on other then /tmp directories (apparmor)

If you get SQL Error: 13 after changing tmpdir parameter in you my.cnf first check permissions in a new directory. If permissions are correct you might be having an issue with AppArmor. AppArmor is a GNU security module for the Linux kernel and it might prevent MySQL from writing to the new directory.

Run: aa-status

To verify if it`s on. If so you will get something like:

profiles are loaded

profiles are in enforce mode

Edit this file:

/etc/apparmor.d/usr.sbin.mysqld

and append your new temp directory in the end.

####

/usr/sbin/mysqld {

...

/new_tmp/ r,

/new_tmp/* rw,

}

Reload AppArmor with:

/etc/init.d/apparmor reload

Thats it.