/dev/dri/card0: failed to set DRM interface version 1.4: Permission denied
RADEON(0): [drm] Failed to open DRM device for pci:0000:01:00.0: No such file or directory
RADEON(0): Kernel modesetting setup failed
Screen(s) found, but none have a usable configuration.

no screens found(EE) 

Please also check the log file at "/var/log/Xorg.0.log" for additional information.

Server terminated with error (1). Closing log file.