问题：正在使用的Linux系统突然有一天不能解析域名gus.xxxxxxxx.com?
# ping gus.xxxxxxxx.com
ping: unknown host gus-xxxxxxxx.com
解决方法：
1、查看/etc/hosts
# cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.1.3 gus.xxxxxxxx.com
2、查看/etc/host.conf
# cat /etc/host.conf order hosts, bind multi on
3、查看/etc/resolv.conf
# cat /etc/resolv.conf search localdomain #nameserver 8.8.4.4 nameserver 8.8.8.8
初始使用的是 “nameserver 8.8.4.4”，导致域名解析错误，后来改为"nameserver 8.8.8.8"就可以正常解析了
#ping gus.xxxxxxxx.com PING gus.xxxxxxxx.com (192.168.1.3) 56(84) bytes of data. 64 bytes from ec192-168-1-3.ap-northeast-2.compute.amazonaws.com (192.168.1.3): icmp_seq=1 ttl=39 time=458 ms