resolv.conf文件中有search项时，主机名解析规则顺序：
DNS配置文件如下：
# vi /etc/resolv.conf
# Generated by NetworkManager
search openstack.local dev.com example.local
nameserver 192.168.122.21例1：查询主机名，因为主机名后面没有点，就认为是主机名，所以先添加search里的每一项依次组成FQDN（完全合格域名）来查询，完全合格域名查询未找到，就再认为主机名是完全合格域名来查询。
# host -a centos7-bind-1
Trying "centos7-bind-1.openstack.local"
Trying "centos7-bind-1.dev.com"
Trying "centos7-bind-1.example.local"
Trying "centos7-bind-1"
;; connection timed out; no servers could be reached
例2：查询主机名，因为主机名中有点（不是末尾有点），就认为是完全合格域名，先用它来查询，查询失败就把它当成是主机名来进行，添加search里的每一项组成FQDN（完全合格域名）来查询。
# host -a centos7-bind-1.com
Trying "centos7-bind-1.com"
Received 109 bytes from 192.168.122.21#53 in 177 ms
Trying "centos7-bind-1.com.openstack.local"
Trying "centos7-bind-1.com.dev.com"
Trying "centos7-bind-1.com.example.local"
Host centos7-bind-1.com not found: 3(NXDOMAIN)
Received 125 bytes from 192.168.122.21#53 in 55 ms
例3：查询主机名，因为主机名中末尾有点，则认为是完全合格域名，只用它来查询（不会再添加search里的每一项）。查询次数会与search里项域名个数有关。
# host -a centos7-bind-1.
Trying "centos7-bind-1"
;; connection timed out; trying next origin
Trying "centos7-bind-1"
;; connection timed out; trying next origin
Trying "centos7-bind-1"
;; connection timed out; trying next origin
Trying "centos7-bind-1"
;; connection timed out; no servers could be reached
原始文章链接:https://blog.csdn.net/hxpjava1/article/details/80179235