I have Chrubuntu installed on my Acer C710-2847.
sudo cgpt add -i 6 -P 0 -S 1 /dev/sda doesn't let me boot into ChromeOS. The machine will continue the Chrubuntu boot... What do I do? I don't want to keep exiting developer mode, just a hassle to have stuff get deleted, etc.
You have to download the package cgpt first. I know it shows that it exists under /usr/bin/cgpt but installing it from here: http://packages.ubuntu.com/raring/amd64/cgpt/download solved my problem. Good luck