Install and configure DNS in Linux

Mar 30, 2021 · 3 mins read

In the video below, we show you how to install and configure DNS server in Linux using Ubuntu 20.04 LTS and Bind

We’ll set up a DNS forwarder for Internet DNS resolution, as well as forward and reverse lookup zones for our local network

Useful links:
https://ubuntu.com/download/server

Installation and configuration example:

Install Ubuntu and apply the latest patches

Install and configure Bind9

sudo apt install -y bind9 bind9utils bind9-doc dnsutils

Configure DNS Forwarding

cd /etc/bind  
Backup the existing file, named.conf.options e.g.  
sudo cp named.conf.options named.conf.options.bak

Edit named.conf.options e.g.

sudo nano named.conf.options

So it looks something like this

acl trustedclients {
	localhost;
	localnets;
	172.16.18.0/24;
	172.16.19.0/24;
};

options {
	directory "/var/cache/bind";

	recursion yes;
	allow-query { trustedclients; };
	allow-query-cache { trustedclients; };
	allow-recursion { trustedclients; };

	forwarders {
		1.1.1.2;
		1.0.0.2;
	};

	dnssec-validation no;

	listen-on-v6 port 53 { ::1; };
	listen-on port 53 { 127.0.0.1; 172.16.17.10; };
};

NOTE: DNSSec disabled as it was found to cause issues for Ubuntu 20.04

Define zone files
Backup the existing file named.conf.local e.g.

sudo cp named.conf.local named.conf.local.bak

Edit named.conf.local e.g.

sudo nano named.conf.local

So it looks something like this

zone "templab.lan" {
	type master;
	file "/etc/bind/db.templab.lan";
};

zone "17.16.172.in-addr.arpa" {
	type master;
	file "/etc/bind/db.172.16.17";
};

Check the file for errors

sudo named-checkconf

Create a forward lookup zone
Copy an existing file to one with the name used before e.g.

sudo cp db.local db.templab.lan

Edit the file e.g.

sudo nano db.templab.lan

So that it looks something like this

;  
; BIND data file for templab.lan zone  
;  
$TTL 604800  
@ 		IN	SOA	ns1.templab.lan. admin.templab.lan. (  
			3; Serial  
			604800; Refresh  
			86400; Retry  
			2419200; Expire  
			604800 ); Negative Cache TTL  
;
@		IN	NS	ns1.templab.lan.  

ns1 	IN 	A 	172.16.17.10
dhcp1 	IN 	A 	172.16.17.12
fw		IN 	A 	172.16.18.254

Check the file syntax

sudo named-checkzone templab.lan db.templab.lan

Create a reverse lookup zone
Copy an existing file to one with the name used before e.g.

sudo cp db.127 db.172.16.17

Edit the file e.g.

sudo nano db.172.16.17

So that it looks something like this

;
; BIND reverse data file for templab.lan zone
;
$TTL 604800
@ 		IN 	SOA 	ns1.templab.lan. admin.templab.lan. (
			2; Serial
			604800; Refresh
			86400; Retry
			2419200; Expire
			604800 ); Negative Cache TTL
;
@ 		IN	NS	ns1.templab.lan.

10		IN 	PTR	ns1.templab.lan.
12		IN	PTR	dhcp1.templab.lan.

Check the file syntax

sudo named-checkzone 17.16.172.in-addr.arpa db.172.16.17

Edit the server’s DNS entry to use it’s own DNS server
```
cd /etc/netplan
```
Edit the yaml configuration file, e.g.
```
sudo nano 00-installer-config.yaml
```
Change the IP address of the dns server entry and save the file
Apply the change
```
sudo netplan apply
```

Start and test DNS

start bind9
sudo systemctl start bind9

Check its status

sudo systemctl status bind9

Test DNS is working e.g.

host dhcp1.templab.lan
host 172.16.17.10
ping www.amazon.com