How To Configure DNS Server On Ubuntu 18.04 / Ubuntu 16.04
Prerequisites
1. A Ubuntu machine (18.04.4 LTS)
2. IP Address 192.168.1.210
3. Hostname (ns1.example.com)
sudo apt update
Install DNS Server
The package name for the DNS server on Ubuntu is bind9 and is available in the base repository. Use the apt command to install the bind9 package.
sudo apt install -y bind9 bind9utils bind9-doc dnsutils
Configure DNS Server
The /etc/bind/ directory is the main configuration directory of the DNS server, and it holds configuration files and zone lookup files.
Global configuration file is /etc/bind/named.conf. You should not use this file for your local DNS zone rather you can use /etc/bind/named.conf.local file.
Create Zones
Let us begin by creating a forward zone for your domain.
sudo nano /etc/bind/named.conf.local
Forward Zone
The following is the forward zone entry for the example.com domain in the named.conf.local file.
zone "example.com" IN { // Domain name type master; // Primary DNS file "/etc/bind/forward.example.com.db"; // Forward lookup file allow-update { none; }; // Since this is the primary DNS, it should be none. };
Reverse Zone
The following entries are for the reverse zone in the named.conf.local file.
zone "1.168.192.in-addr.arpa" IN { //Reverse lookup name, should match your network in reverse order
type master; // Primary DNS
file "/etc/bind/reverse.example.com.db"; //Reverse lookup file
allow-update { none; }; //Since this is the primary DNS, it should be none.
};
Create Zone lookup file
Once you create zones, you can go ahead and create zone data files that hold DNS records for the forward zone and reverse zone.
Forward Zone lookup file
Copy the sample entries to zone file called forward.example.com.db for the forward zone under /etc/bind directory.
Record types in the zone file,
SOA – Start of Authority
NS – Name Server
A – A record
MX – Mail for Exchange
CN – Canonical Name
NS – Name Server
A – A record
MX – Mail for Exchange
CN – Canonical Name
Domain names should end with a dot (.).
sudo cp /etc/bind/db.local /etc/bind/forward.example.com.db
Edit the zone.
sudo nano /etc/bind/forward.example.com.db
Update the content shown below.
Whenever you change any records in the lookup file, make sure you update the serial number to some random number, higher than current.
$TTL 604800
@ IN SOA ns1.example.com. root.example.com. (
3 ; Serial
604800 ; Refresh
86400 ; Retry
2419200 ; Expire
604800 ) ; Negative Cache TTL
;
;@ IN NS localhost.
;@ IN A 127.0.0.1
;@ IN AAAA ::1
;Name Server Information
@ IN NS ns1.example.com.
;IP address of Name Server
ns1 IN A 192.168.1.210
;Mail Exchanger
example.com. IN MX 10 mail.example.com.
;A – Record HostName To Ip Address
www IN A 192.168.1.100
mail IN A 192.168.1.150
;CNAME record
ftp IN CNAME www.example.com.
Reverse Zone lookup file
Copy the sample entries to the zone file called reverse.example.com.db for the reverse zone under /etc/bind directory and create reverse pointers for the above forward zone records.
PTR – Pointer
SOA – Start of Authority
SOA – Start of Authority
sudo cp /etc/bind/db.127 /etc/bind/reverse.example.com.db
Edit the reverse zone file.
sudo nano /etc/bind/reverse.example.com.db
Update the content shown below.
Whenever you change any DNS records in the lookup file, make sure to update the serial number to some random number, higher than the current one.
$TTL 604800
@ IN SOA example.com. root.example.com. (
3 ; Serial
604800 ; Refresh
86400 ; Retry
2419200 ; Expire
604800 ) ; Negative Cache TTL
;
;@ IN NS localhost.
;1.0.0 IN PTR localhost.
;Name Server Information
@ IN NS ns1.example.com.
;Reverse lookup for Name Server
10 IN PTR ns1.example.com.
;PTR Record IP address to HostName
100 IN PTR www.example.com.
150 IN PTR mail.example.com.
Check BIND Configuration Syntax
Use named-checkconf command to check the syntax and named.conf* files for any errors.
sudo named-checkconf
Command will return to the shell if there are no errors.
Also, you can use named-checkzone to check the syntax errors in zone files.
Forward zone
sudo named-checkzone itzgeek.local /etc/bind/forward.example.com.db
Output:
zone example.com/IN: loaded serial 3 OK
Reverse zone
named-checkzone 1.168.192.in-addr.arpa /etc/bind/reverse.example.com.db
Output:
zone 1.168.192.in-addr.arpa/IN: loaded serial 3 OK
Restart bind service.
sudo systemctl restart bind9
Enable it on system startup.
sudo systemctl enable bind9
Check the status of the bind9 service.
sudo systemctl status bind9
DNS Record Update
Whenever you change a DNS record, do not forget to change the serial number in the zone file and reload the zone.
Change example.com & 1.168.192.in-addr.arpa with your zone names.
### Forward Zone ### sudo rndc reload example.com ### Reverse Zone ### sudo rndc reload 1.168.192.in-addr.arpa
Ref:
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