This workaround may be specific to a combination of Macbook Air 6,2 running Ubuntu 14.04 (Trusty).

I've been recently experimenting a lot with Linux Containers, and needed to have access to a native Linux environment. One of the easiest ways I found to achieve this was to boot from a USB 3.0 stick - as this both doesn't take away precious internal storage, and avoiding rEFIt/rEFInd altogether.

There were numerous problems, but one of the more annoying ones was that the backtick and tilde keys were not working as expected. In my case, I was getting < and > instead of backtick and tilde. More on the installing and fixing to be covered in a separate post.

Luckily, there was a workaround:

echo 0 > /sys/module/hid_apple/parameters/iso_layout

(You will need to add this to somewhere like /etc/rc.local to make it permanent.)

Source: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1245081