I wanted to install Ubuntu in an external HDD to boot it from my Macbook Pro. After following Coljac's response at: How to boot Ubuntu on a mac from external USB storage?
I've found that my computer no longer boots by default on MacOS X, but instead shows a GRUB prompt. I can still access the original boot menu if I press Alt after powering the computer on, but I would like the boot to behave as it used to.
How may I get back to that configuration without breaking my Ubuntu boot on the external HDD?