[libvirt] Problems with <filesystem type='block'>

Using libvirt 1.0.1, I'm trying to start an LXC container using the '<filesytem type="block">' syntax, like this: <filesystem type="block" accessmode="passthrough"> <source dev="/dev/vg_files/vm-foobar-root" /> <target dir="/" /> </filesystem> The specified block device exists: # ls -lL /dev/vg_files/vm-foobar-root brw-rw---- 1 root disk 253, 19 Dec 21 22:23 /dev/vg_files/vm-foobar-root If I start the domain, it appears to start without any errors... # virsh start foobar Domain foobar started ...but it's not actually running. The log files (with loglevel=2) don't seem to be very interesting; this is everything from the instance log file: 2012-12-22 04:10:57.862+0000: starting up PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin LIBVIRT_DEBUG=2 LIBVIRT_LOG_OUTPUTS=2:stderr /usr/lib/libvirt/libvirt_lxc --name foobar --console 22 --security=none --handshake 25 --background --veth veth1 2012-12-22 04:10:57.967+0000: 1468: info : libvirt version: 1.0.1 2012-12-22 04:10:57.967+0000: 1468: info : lxcCapsInit:151 : No driver, not initializing security driver PATH=/bin:/sbin TERM=linux container=lxc-libvirt container_uuid=9041e32e-1df2-00c2-4660-dfa5b41510b7 LIBVIRT_LXC_UUID=9041e32e-1df2-00c2-4660-dfa5b41510b7 LIBVIRT_LXC_NAME=foobar /sbin/init 2012-12-22 04:10:58.198+0000: 1: warning : lxcContainerDropCapabilities:1788 : libcap-ng support not compiled in, unable to clear capabilities 2012-12-22 04:10:58.198+0000: 1493: warning : lxcControllerClearCapabilities:679 : libcap-ng support not compiled in, unable to clear capabilities Running an "strace" on the libvirtd process (strace -p <libvirtd_pid> -f ...), it doesn't look like libvirt is ever trying to mount the referenced filesystem. Is this supposed to work? It seems like the support for having libvirt mount the block device is relatively recent, and I haven't had much luck finding examples of other folks using this capability. Thanks, -- Lars