Comment 4 for bug 307845

Maybe I should've been more specific. Currently, when you boot a KVM
based virtual machine with virtio based block device configured, there
will be /dev/vd[a-z] block device nodes available for disks that were
attached when you first booted. However, if you hot-plug new disks to
the VM by e.g. running command attach-disk in virsh management utility,
and the kernel is configured to detect plugging of disks (default
Intrepid kernel will work just fine as long as acpiphp
module is loaded), no block device for the disk is created under /dev.
udev does not know about these vd* disks and thus no new /dev/vd*
device is created for the newly plugged in disk. Thus you can't actually
access the new disk for e.g. partitioning it since there's no
corresonding block device available. With this patch applied to the rule
file, udev will create /dev/vd* block device for the new disk as
expected, as it does when e.g. a FireWire or USB disk is plugged in, and
you can partition the disk with fdisk or do what ever you normally do
with a block device node. I don't care where this rule should be put,
go ahead and implement functionally equivalent fix somewhere else,
it's just that current udev in Ubuntu does not work as it should.