Technical Information: DNS Services on Ubuntu Server

A nice reference for configuration of bind on Ubuntu server

Config files are under: /etc/bind

In named.conf.options:

• Add an ACL section above the “options” section:

  acl "trusted" {
  	192.168.0.123;
  	192.168.0.8;
  	192.168.0.12;
  	192.168.0.220;
  };

• Add to “options” section (after “directory”):

  	recursion yes;
  	allow-recursion { trusted; };
  	listen-on { 192.168.0.123; };
  	allow-transfer { none; };

• Uncomment the “forwarders” section, and add upstream DNS servers to it

In named.conf.local:

• Add zone(s) for local network/subnets:

  zone "samudio.net" {
  	type master;
  	file "/etc/bind/zones/db.samudio.net";
  	allow-transfer { 192.168.0.8; };		# ns2 private IP address - secondary
  };

• Add reverse zone(s):

  zone "168.192.in-addr.arpa" {
  	type master;
  	file "/etc/bind/zones/db.168.192";
  	allow-transfer { 192.168.0.8; };		# ns2 private IP address - secondary
  };

Create forward zone file:

• cd /etc/bind ; mkdir zones ; cp db.local zones/db.samudio.net
• Edits to forward zone file (/etc/bind/zones/db.samudio.net)

  @    IN    SOA   ns1.samudio.net. admin.samudio.net. (
  			3        ; Serial
  ; name servers - NS records
  	IN    NS    ns1.samudio.net.
  	IN    NS    ns2.samudio.net.
  ; 192.168.0.0/24 - A records
  	host1.samudio.net.    IN    A    192.168.0.101
  	host2.samudio.net.    IN    A    192.168.0.102

Create reverse zone file(s):

• cd /etc/bind/zones ; cp ../db.127 ./db.168.192
• Edits to reverse zone file(s):

  @    IN    SOA   ns1.samudio.net. admin.samudio.net. (
  			3        ; Serial
  ; name servers - NS records
  	IN    NS    ns1.samudio.net.
  	IN    NS    ns2.samudio.net.
  ; PTR records
  	123.0    IN    PTR    ns1.samudio.net.    ; 192.168.0.123
  	125.0    IN    PTR    ns2.samudio.net.    ; 192.168.0.125
  	101.0    IN    PTR    host1.samudio.net.  ; 192.168.0.101
  	102.0    IN    PTR    host2.samudio.net.  ; 192.168.0.102

Check BIND configuration syntax, zone(s), and reverse zone(s):

• named-checkconf
• named-checkzone samudio.net db.samudio.net
• named-checkzone 168.192.in-addr.arpa /etc/bind/zones/db.168.192

Restart BIND: systemctl restart bind9

Secondary DNS server differences:

• The forwarders section in named.conf.options should contain 8.8.8.8 and similar
• In named.conf.local, type should be “slave”, with masters pointing to primary

  zone "samudio.net" {
  	type slave;
  	file "slaves/db.samudio.net";
  	masters { 192.168.0.123; };	# ns1
  };

  zone "168.192.in-addr.arpa" {
  	type slave;
  	file "slaves/db.168.192";
  	masters { 192.168.0.123; };	# ns1
  };

If using UFW firewall, remember to update rules (on all DNS servers): ufw allow Bind9

On clients, in /etc/network/interfaces:

	dns-nameservers 192.168.0.123 192.168.0.125 8.8.8.8
	dns-search samudio.net

Refresh network interface (on clients): ifdown –force eth0 && ip addr flush dev eth0 && ifup –force eth0

Check /etc/resolv.conf on client for correct update, should look like:

	nameserver 192.168.0.123
	nameserver 192.168.0.125
	nameserver 8.8.8.8
	search samudio.net

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