openstack 虚拟机迁移时应注意的问题

（1） hostname 以及hosts文件

（2）libvirt的配置 以及权限

def migrate_disk_and_power_off(self, context, instance, dest,
                                   instance_type, network_info,
                                   block_device_info=None):
        LOG.debug(_("Starting migrate_disk_and_power_off"),
                   instance=instance)
        disk_info_text = self.get_instance_disk_info(instance['name'])
        disk_info = jsonutils.loads(disk_info_text)
        self.power_off(instance)
        block_device_mapping = driver.block_device_info_get_mapping(
            block_device_info)
        for vol in block_device_mapping:
            connection_info = vol['connection_info']
            mount_device = vol['mount_device'].rpartition("/")[2]
            self.volume_driver_method('disconnect_volume',
                                      connection_info,
                                      mount_device)
        # copy disks to destination
        # rename instance dir to +_resize at first for using
        # shared storage for instance dir (eg. NFS).
        same_host = (dest == self.get_host_ip_addr())
        inst_base = libvirt_utils.get_instance_path(instance)
        inst_base_resize = inst_base + "_resize"
        try:
            utils.execute('mv', inst_base, inst_base_resize)
            if same_host:
                dest = None
                utils.execute('mkdir', '-p', inst_base)
            else:
                utils.execute('ssh', dest, 'mkdir', '-p', inst_base) //需确保各主机之间可以无密码登陆
            for info in disk_info:
                # assume inst_base == dirname(info['path'])