Greeter Application appears to be crashing. Attempting to use a different one

Before the login screen appears in Fedora, you may get a popup saying "Greeter Application appears to be crashing. Attempting to use a different one". You may think, this could be due to video driver fault. In most of the cases, it is because your root directory "/" is 100% full. When you free you space in the "/" drive, the problem goes away.