Cinnamon does not work well with gdm. And there is no meaning to use gdm when using Cinnamon. On Fedora, the default one id gdm. How to replace gdm with lightdm on Fedora?
lightdm if it is not installed yet:
# yum install lightdm lightdm-gtk
gdm service and make the lightdm service be started by systemd
# systemctl disable gdm.service # systemctl enable lightdm.service
After rebooting your Fedora Linux, lightdm should be the dm.
Thank you!!! I am running Fedora 22 in virtualbox, and Cinnamon was complaining about running in “software rendering mode”. I tried downgrading GDM, downgrading mesa, and all the other advice on the web, but the above info fixed it.