Did a perfect install of ubuntu 16.04 to hard drive but can't access. No errors at all went straight thru install to final message that said to reboot to take effect. Reboot and it doesn't go to ubuntu. It was a dual boot with an old copy of Yellow Dog. Also tried to install ubuntu only and same problem. Is there a command line I can enter in open firmware to access ubuntu. When I reboot it goes to Yellow Dog.