I have installed ubuntu alongside os x. I can start it by pressing the option key during startup and choose the correct disk. Everything works.
Now I want to default the ubuntu disk. That works by pressing "Control" while choosing the disk in the startup manager and pressing enter.
My mac now boots default to ubuntu. But it does not work anymore. The login screen appears, but neither keyboard nor touchpad work. Also if I plug in an usb mouse, it does not light up.