'Initialization for a standalone compute service.'

def init_host(self):

    if CONF.pci.passthrough_whitelist:
        whitelist.Whitelist(CONF.pci.passthrough_whitelist)
    if (CONF.placement.os_region_name is None):
        raise exception.PlacementNotConfigured()
    self.driver.init_host(host=self.host)
    context = nova.context.get_admin_context()
    instances = objects.InstanceList.get_by_host(context, self.host, expected_attrs=['info_cache', 'metadata'])
    if CONF.defer_iptables_apply:
        self.driver.filter_defer_apply_on()
    self.init_virt_events()
    try:
        self._destroy_evacuated_instances(context)
        for instance in instances:
            self._init_instance(context, instance)
    finally:
        if CONF.defer_iptables_apply:
            self.driver.filter_defer_apply_off()
        if instances:
            self._update_scheduler_instance_info(context, instances)
