在nagios的几个触发参数里会有w、d、u、f这样的调用方式。具体每个字母代表的意思如下：
host_notification_options： d = notify on DOWN host states, u = notify on UNREACHABLE host states r = notify on host recoveries (UP states) f = notify when the host starts and stops flapping s = send notifications when host or service scheduled downtime starts and ends n (none) as an option, the contact will not receive any type of host notifications. service_notification_options: w = notify on WARNING service states u = notify on UNKNOWN service states c = notify on CRITICAL service states r = notify on service recoveries (OK states) f = notify when the service starts and stops flapping n (none) as an option, the contact will not receive any type of service notifications. 常用的设置 host_notification_options：d,u,r service_notification_options:w,u,c,r