if there is no fb0 device in /dev/ dirctory , you should modify the file in /boot/grub/memu.lst
add vga=0x317 after kernel field then reboot your system.(I use vmware & fc7)
(!) DirectFB/Core: Could not initialize 'system_core' core!
--> Initialization error!
(#) DirectFBError [DirectFBCreate() failed]: Initialization error!,