All, I've spent quite a few hours trying to figure this out to no avail... I have two machines and the result is the same on both. Additionally, each machine does not support full hardware virtualization... I am able to create 8 VMs. When attempting to create ninth VM, I get the following error: Error: Device 51712 (vbd) could not be connected. /etc/xen/scripts/block failed; error detected. To create the VMs, I use the command: "xm create [vm name]" My machine has 8 GB RAM and is an "old school" dual opteron box. "uname -a" is: Linux centos-host-2 2.6.18-274.3.1.el5.centos.plusxen #1 SMP Wed Sep 7 06:25:54 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux To be clear, I can shutdown any one of the 8 VMs and then run the ninth "xm create" - that VM will start... I did some google'ing and from what I cn tell that error arises due to the lack of loop back devices (there being 8 by default)... I've tried both using MAKEDEV (in my /etc/rc.local) to create a number of loop back devices and put max_loops in my grub,.conf file. For example here is what I have in grub.conf now: title CentOS (2.6.18-274.3.1.el5.centos.plusxen) root (hd0,0) kernel /xen.gz-2.6.18-274.3.1.el5.centos.plus module /vmlinuz-2.6.18-274.3.1.el5.centos.plusxen ro root=LABEL=/ max_loop=64 module /initrd-2.6.18-274.3.1.el5.centos.plusxen.img Due to wrapping, max_loop is actually on the module /vmlinuz- line... I also tried to put max_loop on the kernel line as well... As I mentioned above, I also created the loop back devices from /etc/rc.local like so: /sbin/MAKEDEV -d /dev -m 64 loop And, once I can log in to the machine, I do see everything in /dev (for example /dev/loop0 to /dev/loop64) Has anyone else had this problem? If so, how did you resolve it???? Thanks ahead of time!!!!! Scot P. Floess RHCT (Certificate Number 605010084735240) Chief Architect FlossWare http://sourceforge.net/projects/flossware http://flossware.sourceforge.net https://github.com/organizations/FlossWare