On 09/18/2013 01:43 AM, yue wrote: Have you checked all the obvious suspects? For example, do you need to enable virt_use_nfs to let SELinux be happy with your setup? Have you double-checked the backing chain for correctness? Have you checked the output of 'qemu-img info /rhev/data-center/7828f2ae-955e-4e4b-a4bb-43807629dc52/d028d521-d4a9-4dd7-a0fe-3e9b60e7c4e4/images/ac025dc1-4e25-4b71-8c56-88dcb61b9f09/cae1bb2d-0529-4287-95a3-13dcb14f082f', repeated for each backing file listed until you get a listing with no backing file? In particular, make sure that every image in the chain properly lists the backing file format (if any image in the chain doesn't list the backing file format, then libvirt treats it as raw for security reasons, and doesn't grant qemu access rights to follow the chain any further, which is one reason for seeing a message such as this). Can you reproduce it using latest libvirt.git instead of pre-built? This list focuses on upstream development, and since you are using an older CentOS build, it is not entirely obvious whether your problem is something that only downstream will suffer (because it may have already been fixed upstream). If you were actually using RHEV instead of CentOS, this would be a perfect opportunity for you to take advantage of your Red Hat support contract and get someone to help you work through it, instead of being told that you are somewhat on your own. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org