1. I am using libvirt 0.8.3 on fedora14 . Acoording to http://berrange.com/posts/2009/12/03/using-cgroups-with-libvirt-and-lxckvm-guests-in-fedora-12/ inorder to have libvirt memory cgroup under a pre specified group one should add CGROUP_DAEMON="memory:/virt" to /etc/sysconfig/libvirtd and restart cgconfig service and the libvirtd service . That did not help . any idea ? 2. Also : specifying a limit to the memory subsystem (/dev/cgroup/memory/libvirt/qemu/memory.limit_in_bytes) by echoing a value , does not propagate to a VM generated later under qemu which is actually generated with a huge default value for memory.limit_in_bytes . Suppose there was such a limit . Should it decline a generation of a VM that requests a higher memory size in its XML file or the limit prevents the VM from consuming more that the specified cgroup limit when consuming a higher value thanks Zvi Dubitzky Email:dubi at il.ibm.com