sudo mknod ./xvda  b 202  0
sudo mknod ./xvda1 b 202  1
sudo mknod ./xvda2 b 202  2
sudo mknod ./xvdb  b 202 16
sudo mknod ./xvdb1 b 202 17
sudo mknod ./xvdb2 b 202 18
sudo mknod ./xvdc  b 202 32
sudo mknod ./xvdc1 b 202 33
sudo mknod ./xvdc2 b 202 34
-----
def blkdev_name_to_number(name):
    """Take the given textual block-device name (e.g., '/dev/sda1',
    'hda') and return the device number used by the OS. """

    n = expand_dev_name(name)

    try:
        return os.stat(n).st_rdev
    except Exception, ex:
        pass