No, I just had to put it in developer mode. Same story on a more recent Chromebook which was Atom-based. Some Chromebooks require a hardware mod before you can install Linux; you have to open them up and set a jumper (or something), but both of mine didn't require that.

Here are the directions I used for my Samsung ARM Chromebook. These directions are probably obsolete for more modern hardware, so take them with a grain of salt:

http://chromeos-cr48.blogspot.com/2013/05/chrubuntu-one-scri...