Question

Change DNS server with bash

Posted October 8, 2016 23.1k views
Networking DNS Ubuntu 16.04

Hello,

To change DNS server you must change the values in /etc/network/interfaces. But the server I’m setting up is being up up by a Bash script, I need to be able to change the DNS server thru Bash.

Anyone having an idea how that can be done?

These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.

3 answers

Hello @Geekologist,

By default on DigitalOcean Ubuntu 16.04 /etc/network/interfaces is populated with Google Public DNS - 8.8.8.8 - 8.8.4.4.
If you open etc/network/interfaces with any text editor you will see following:

# This file describes the network interfaces available on your
# system and how to activate them. For more information, see
# interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
        address 111.111.111.111
        netmask 255.255.255.0
        gateway 111.111.111.0
        up ip addr add 10.17.0.6/16 dev eth0
        dns-nameservers 8.8.8.8 8.8.4.4

Red values could be different in you case.
Note the dns-nameservers 8.8.8.8 8.8.4.4 - it says to use Google Public DNS.
You can change it with simple command - sed.

  • sed -i '/dns-nameservers 8.8.8.8 8.8.4.4/c\ dns-nameservers 1.2.3.4 1.2.3.5' /etc/network/interfaces

You can learn more about sed at GNU docs
Change red values in command to reflect your desired DNS settings. After you execute it, it will change values.
When you open /etc/network/interfaces you will notice changes.

You can also use this as User data on Droplet Creation:

#!/bin/bash

sed -i '/dns-nameservers 8.8.8.8 8.8.4.4/c\        dns-nameservers 1.2.3.4 1.2.3.4' /etc/network/interfaces

Note: this applies for DigitalOcean Ubuntu 16.04 droplets. If you use another host, or using it on your own machine, /etc/network/interfaces could be different and can cause command to fail!

Tell me please, when you change DNS, can also change my ip address? Or two of these parameters are not interrelated?

  • Sorry, not following your question?

  • IP address and DNS server is not the same thing and not so relevant to each other.

    Under /etc/network/interfaces you can see IP address and it is usually your Droplet Public IP. You can’t change Droplet Public IP, it is assigned on Droplet creation and that’s it.
    In case you want to change Droplet Public IP you would have to take a snapshot of Droplet and create new Droplet from that snapshot. Then you can destroy old Droplet and continue to use new one.

    DNS server is used for DNS lookup queries. It resolves domain names to IP addresses. So when you type digitalocean.com in browser or ping it, it will return DigitalOcean IP address.
    There are many DNS servers but most popular is Google Public DNS which is free and accessible via 8.8.8.8 and 8.8.4.4.

Submit an Answer