######## ON Cent OS 7##################
yum install bind bind-utils bind-chroot  

systemctl enable named
systemctl start  named

#change lines as following
listen-on port 53 {any;};
listen-on-v6  port 53	{none;};
allow-query  {any;};

#after configuring
named-checkconf
systemctl reload named

#define zone on /etc/named.conf as bellow
zone "iran.ir" {
	type master;
	file "iran.ir.db";
};

#after configuring
cp $(rpm -qa bind | grep localhost | head -1) /var/named/iran.ir.db

#configuring /var/named/iran.ir.db as bellow
$TTL 1D
@	IN	SOA	iran.ir.	admin.iran.ir.	(
					0	; serial
					1D	; refresh
					1H	; retry
					1W	; expire
					3H )	; minimum
	NS	@
	A	127.0.0.1
	AAAA	::1
ns1	A	192.168.61.143
www	A	192.168.61.150
w	CNAME	www.iran.ir.
ww	CNAME	www.iran.ir.
mail1	A	192.168.61.120
@	MX	0	mail1.iran.ir.

#after configuration
named-checkzone iran.ir	/var/named/iran.ir.db
systemctl reload named

#for verification 
rndc flush
dig @localhost A iran.ir

######## ON Ubuntu 20.04 ##############
apt-get update && apt-get install bind9 bind9-utils

#add following line into /etc/bind/named.conf
zone "iran.ir." {
	type	master;
	file	"iran.ir.db";
};

#after add configuration to verfiy
named-checkconf

#add following line into /var/cache/bind/iran.ir.db
$TTL 1D
@       IN      SOA     iran.ir.        admin.iran.ir.  (
                                        0       ; serial
                                        1D      ; refresh
                                        1H      ; retry
                                        1W      ; expire
                                        3H )    ; minimum
        NS      @
        A       127.0.0.1
        AAAA    ::1
ns1     A       192.168.61.143
www     A       192.168.61.150
w       CNAME   www.iran.ir.
ww      CNAME   www.iran.ir.
mail1   A       192.168.61.120
@       MX      0       mail1.iran.ir.

#change user permission of iran.ir.db
chown bind:bind /var/cache/bind/iran.ir.db

#and check configuration with following command
named-checkzone iran.ir /var/cache/bind/iran.ir.db

#reload service and verfy dns service
systemctl reload named

rndc flush
dig @localhost A iran.ir