Ubuntu中设置永久的DNS

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由于公司的服务基本都是ubuntu的，大部分和centos差不多，还是有区别的。如下记录修改DNS
root@ubuntu:~# cat /etc/resolvconf/resolv.conf.d/base #（这个文件默认是空的）
nameserver 218.2.2.2
nameserver 223.5.5.5　　#新插入的DNS说明

• 　　218.2.2.2 是南京电信的DNS
  
• 　　223.5.5.5 是阿里的DNS
  
• 　　如果有多个DNS就一行一个
  

　　

　　修改好以后重新加载，执行resolvconf -u
root@ubuntu:~# sudo resolvconf -u
root@ubuntu:~# cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 218.2.2.2
nameserver 223.5.5.5可以看到我们的设置已经加上了，然后再ping一个域名，当时就可以解析了，无需重启。
root@ubuntu:~# ping -c4 baidu.com
PING baidu.com (111.13.101.208) 56(84) bytes of data.
64 bytes from 111.13.101.208: icmp_seq=1 ttl=50 time=25.0 ms
64 bytes from 111.13.101.208: icmp_seq=2 ttl=50 time=26.0 ms
64 bytes from 111.13.101.208: icmp_seq=3 ttl=50 time=24.8 ms
64 bytes from 111.13.101.208: icmp_seq=4 ttl=50 time=25.6 ms
--- baidu.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3006ms
rtt min/avg/max/mdev = 24.812/25.380/26.025/0.503 ms　　此时若是还是不能ping外网，在查查你的网关
　　我举个例子，删除了我默认网关，然后添加上就OK了
root@ubuntu:/home/leco# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.5.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
root@ubuntu:/home/leco# sudo route add default gw 192.168.5.1
root@ubuntu:/home/leco# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.5.1     0.0.0.0         UG    0      0        0 eth0
192.168.5.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
root@ubuntu:/home/leco# ping 117.185.7.45
PING 117.185.7.45 (117.185.7.45) 56(84) bytes of data.
64 bytes from 117.185.7.45: icmp_seq=1 ttl=50 time=10.1 ms
^C
--- 117.185.7.45 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 10.179/10.179/10.179/0.000 ms
root@ubuntu:/home/leco# ping baidu.com
PING baidu.com (180.149.132.47) 56(84) bytes of data.
64 bytes from 180.149.132.47: icmp_seq=1 ttl=55 time=24.1 ms
^C
--- baidu.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 24.181/24.181/24.181/0.000 ms