Changing DNS server and nslookup on ubuntu

Posted under » Ubuntu » Linux on 1 August 2017

Sometimes out of a sudden, your internet simply would not work. Most probably because your DNS settings are wrong. A simple delete of /etc/resolv.conf and a reboot should fix it.

However, if it still does not work, then force delete and edit the file like so.

$ rm -f /etc/resolv.conf
$ vim /etc/resolv.conf

First is to remove the softlink /etc/resolv.conf, a file that is generated automatically. The contents of the new /etc/resolv.conf, assuming you want to use google DNS.

nameserver 8.8.8.8
nameserver 8.8.4.4

Now disable DNSMasq by commenting it out in /etc/NetworkManager/NetworkManager.conf. Mine look like this.

[main]
plugins=ifupdown,keyfile,ofono
#dns=dnsmasq

no-auto-default=10:0C:29:69:C5:EF,

[ifupdown]
managed=false

Now restart the NetworkManager

$ service network-manager restart

You can check what DNS is working by

$ nmcli device show | grep IP4.GATE

If you still showing the default localhost or router, try nslookup. It should look like this

$ nslookup anoneh.com
Server:         8.8.8.8
Address:        8.8.8.8#53

Non-authoritative answer:
Name:   anoneh.com
Address: 132.147.91.14

You can select a particular DNS server to query

$ nslookup
> server 8.8.8.8
Default Server : dns.google
Address : 8.8.8.8

> anoneh.com
Server:         8.8.8.8
Address:        8.8.8.8#53

Non-authoritative answer:
Name:   anoneh.com
Address: 132.147.91.14

You can achieve similar results with the dig command.

You can also use the following online tools and this.

If you want to clear your DNS cache

$ systemd-resolve --flush-caches

For network tools.