所有域名无法正常解析。
- ping www.baidu.com 等域名提示 Temporary failure in name resolution错误。
root@localhost:~# ping www.baidu.com
ping: www.baidu.com: Temporary failure in name resolution
root@localhost:~# 一、ubuntu/debian（emporary failure in name resolution）
1、修改/etc/resolv.conf配置文件
sudo vim /etc/resolv.conf 添加如下内容：nameserver 8.8.8.8
然后重新试下，访问正常
root@localhost:~# ping www.baidu.com
PING www.a.shifen.com (39.156.66.18) 56(84) bytes of data.
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=1 ttl=52 time=21.9 ms
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=2 ttl=52 time=21.8 ms
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=3 ttl=52 time=37.3 ms
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=4 ttl=52 time=23.0 ms
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=5 ttl=52 time=32.4 ms
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=6 ttl=52 time=42.5 ms
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=7 ttl=52 time=22.0 ms
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=8 ttl=52 time=25.9 ms
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=9 ttl=52 time=22.1 ms
64 bytes from 39.156.66.18 (39.156.66.18): icmp_seq=10 ttl=52 time=42.2 ms
^C
--- www.a.shifen.com ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 28ms
rtt min/avg/max/mdev = 21.801/29.118/42.487/8.263 ms
root@localhost:~# 二、 CentOS（Couldn’t resolve host）
CentOS 下面直接修改
/etc/resolv.conf不行，因为该文件调用了/etc/sysconfig/network-scripts/ifcfg-eth0的配置预设，既然知道了这两个文件的工作原理，那么我们必须要在/etc/sysconfig/ network-scripts/ifcfg-eth0里面最后加上 dns 地址让resolv.conf来调用。否则重启后，因为 eth0 中没有预设 dns 的相关信息，就会使/etc/resolv.conf恢复到原来的状态，解析还是不成功。
修改 /etc/sysconfig/network-scripts/ifcfg-eth0 文件
最后加上两行
DNS1=8.8.8.8
DNS2=8.8.4.4
改完后重启网卡
service network restart
重启后再查看 /etc/resolv.conf 文件是这样的：
# Generated by NetworkManager
search webhostbox.net
nameserver 8.8.8.8
