I know that this post is old, but this still comes up in search results. I couldn’t find the solution to this problem online, so I ended up figuring it out myself. If you’re using Ubuntu, then there is a program called “Apparmor” that is preventing MySQL from seeing the file. Here’s what you need to do if you want MySQL to be able to read files from the “tmp” directory:
sudo vim /etc/apparmor.d/usr.sbin.mysqld
Once you are in the file, you’re going to see a bunch of directories that MySQL can use. Add the line /tmp/** rwk to the file (I am not sure that it matters where, but here is a sample of where I put it):
/etc/mysql/*.pem r,
/etc/mysql/conf.d/ r,
/etc/mysql/conf.d/* r,
/etc/mysql/*.cnf r,
/usr/lib/mysql/plugin/ r,
/usr/lib/mysql/plugin/*.so* mr,
/usr/sbin/mysqld mr,
/usr/share/mysql/** r,
/var/log/mysql.log rw,
/var/log/mysql.err rw,
/var/lib/mysql/ r,
/var/lib/mysql/** rwk,
/tmp/** rwk,
/var/log/mysql/ r,
/var/log/mysql/* rw,
/var/run/mysqld/mysqld.pid w,
/var/run/mysqld/mysqld.sock w,
/run/mysqld/mysqld.pid w,
/run/mysqld/mysqld.sock w,
Now all you need to do is reload Apparmor:
sudo /etc/init.d/apparmor reload
Note I used “vim”, but substitute that with whatever your favorite text editor is that you know how to use.