disable nouveau

linux /vmlinuz-3.15.4-200.fc20.x86_64 root=UUID=8abb3dc5-d948-4941-92ce-690339d445e5 ro rootflags=subvol=root vconsole.font=latarcyrheb-sun16 rhgb quiet nouveau.modeset=0

add nouveau.modeset=0  to the end of  /boot/grub2/grub.cfg

change runlevel in fedora

With systemd, to switch runlevels:

Code:
systemctl isolate multi-user.target

or ++

systemctl isolate graphical.target

To change the default runlevel:

Code:
rm /etc/systemd/system/default.target
ln -sf /lib/systemd/system/multi-user.target /etc/systemd/system/default.target

or 

ln -sf /lib/systemd/system/graphical.target /etc/systemd/system/default.target

systemd does not even use the /etc/inittab So changing it in there doesn't work anymore.