ntpdate更新系统时间时报错Can't find host ntp1.aliyun.com: Servname not supported for ai_socktype (-8)

所报错误：

[root@web01 ~]# ntpdate ntp1.aliyun.com

Error resolving ntp1.aliyun.com: Servname not supported for ai_socktype (-8)

11 Feb 20:58:03 ntpdate[3318]: Can't find host ntp1.aliyun.com: Servname not supported for ai_socktype (-8)

11 Feb 20:58:03 ntpdate[3318]: no servers can be used, exiting

原因：/etc/services 文件被改动或者不存在导致域名解析错误

[root@web01 etc]# ls -l servic*

-rw-r--r--. 1 root root  10240 Feb 11 02:27 services

-rw-r--r--  1 root root 641020 Feb 11 02:22 services.bak  长格式对比后发现源文件已改动

[root@web01 etc]# mv services /tmp

[root@web01 etc]# ls -l servic*

-rw-r--r-- 1 root root 641020 Feb 11 02:22 services.bak

[root@web01 etc]# mv services.bak  services

[root@web01 etc]# ls -l servic*

-rw-r--r-- 1 root root 641020 Feb 11 02:22 services

[root@web01 etc]# ntpdate ntp1.aliyun.com

12 Feb 17:00:54 ntpdate[3363]: step time server 182.92.12.11 offset 71111.641937 sec