Ubuntu中设置永久的DNS

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