Profile f15.cfg ( to install)  :- name="VF15PV" memory=2048 disk = ['phy:/dev/sda6,xvda,w' ] vif = [ 'bridge=br0' ] # vfb = [ 'type=vnc,vncunused=1'] kernel = "/root/vms/f15/vmlinuz" ramdisk = "/root/vms/f15/initrd.img" vcpus=2 on_reboot = 'restart' on_crash = 'restart' works fine for # xl create f15.cfg -c or # xm create f15.cfg -c As soon as i add "vfb"  line . 1. xl fails when parsing 2. xm reports name "VF15PV" doesn't exist. Runtime profile :- name="VF15PV" memory=2048 disk = ['phy:/dev/sda6,xvda,w' ] vif = [ 'bridge=br0,mac=00:16:3E:66:61:B1' ] bootloader = "/usr/lib/xen-4.1/bin/pygrub" vcpus=2 on_reboot = 'restart' on_crash = 'restart' behaves same way .  No vfb line, then xl and xm works fine. Boris.