DNS, Domain Name System, translates hostnames or URLs into IP addresses. For example if we type www.unixmen.com in browser, the DNS server translates the domain name into its associated ip address. Since the IP addresses are hard to remember, DNS servers are used to translate the hostnames like www.unixmen.com to 173.xxx.xx.xxx. So it makes easy to remember the domain names instead of its IP address.
DNS Server Installation in CentOS 6.5/6.4/6.3
Scenario
Primary(Master) DNS Server Details:
Operating System   : CentOS 6.5 server Hostname       : masterdns.unixmen.local IP Address      : 192.168.1.100/24
Secondary(Slave) DNS Server Details:
Operating System   : CentOS 6.5 server Hostname       : secondarydns.unixmen.local IP Address      : 192.168.1.101/24
Client Details:
Operating System   : CentOS 6.5 Desktop  Hostname       : Client.unixmen.local IP Address      : 192.168.1.102/24
Setup Primary(Master) DNS Server
[[email protected] ~]# yum install bind* -y
1. Configure DNS Server
Add the lines as shown below in ‘/etc/named.conf’ file
[[email protected] ~]# vi /etc/named.conf // // named.conf // // Provided by Red Hat bind package to configure the ISC BIND named(8) DNS // server as a caching only nameserver (as a localhost DNS resolver only). // // See /usr/share/doc/bind*/sample/ for example named configuration files. // options { listen-on port 53 { 127.0.0.1; 192.168.1.100; }; ### Master DNS IP ### listen-on-v6 port 53 { ::1; }; directory "/var/named"; dump-file "/var/named/data/cache_dump.db";     statistics-file "/var/named/data/named_stats.txt";     memstatistics-file "/var/named/data/named_mem_stats.txt"; allow-query   { localhost; 192.168.1.0/24; }; ### IP Range ### allow-transfer{ localhost; 192.168.1.101; }; ### Slave DNS IP ### recursion yes; dnssec-enable yes; dnssec-validation yes; dnssec-lookaside auto; /* Path to ISC DLV key */ bindkeys-file "/etc/named.iscdlv.key"; managed-keys-directory "/var/named/dynamic"; }; logging {     channel default_debug {         file "data/named.run";         severity dynamic;     }; }; zone "." IN { type hint; file "named.ca"; }; zone"unixmen.local" IN { type master; file "forward.unixmen"; allow-update { none; }; }; zone"1.168.192.in-addr.arpa" IN { type master; file "reverse.unixmen"; allow-update { none; }; }; include "/etc/named.rfc1912.zones"; include "/etc/named.root.key";
2. Create Zone files
Create forward and reverse zone files which we mentioned in the ‘/etc/named.conf’ file.
2.1 Create Forward Zone
Create forward.unixmen file in the ‘/var/named’ directory.
[[email protected] ~]# vi /var/named/forward.unixmen $TTL 86400 @  IN  SOA   masterdns.unixmen.local. root.unixmen.local. (     2011071001  ;Serial     3600     ;Refresh     1800     ;Retry     604800    ;Expire     86400    ;Minimum TTL ) @    IN  NS      masterdns.unixmen.local. @    IN  NS      secondarydns.unixmen.local. @    IN  A      192.168.1.100 @    IN  A      192.168.1.101 @    IN  A      192.168.1.102 masterdns    IN  A  192.168.1.100 secondarydns   IN  A  192.168.1.101 client      IN  A  192.168.1.102
2.2 Create Reverse Zone
Create reverse.unixmen file in the ‘/var/named’ directory.
[[email protected] ~]# vi /var/named/reverse.unixmen $TTL 86400 @  IN  SOA   masterdns.unixmen.local. root.unixmen.local. (     2011071001  ;Serial     3600     ;Refresh     1800     ;Retry     604800    ;Expire     86400    ;Minimum TTL ) @    IN  NS      masterdns.unixmen.local. @    IN  NS      secondarydns.unixmen.local. @    IN  PTR     unixmen.local. masterdns    IN  A  192.168.1.100 secondarydns   IN  A  192.168.1.101 client      IN  A  192.168.1.102 100   IN  PTR     masterdns.unixmen.local. 101   IN  PTR     secondarydns.unixmen.local. 102   IN  PTR     client.unixmen.local.
3. Start the DNS service
[[email protected] ~]# service named start Starting named: Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â [ Â OK Â ] [[email protected] ~]# chkconfig named on
4. Adjust iptables to allow DNS server from outside of the network
Add the lines as shown below in ‘/etc/sysconfig/iptables’ file.
[[email protected] ~]# vi /etc/sysconfig/iptables # Firewall configuration written by system-config-firewall # Manual customization of this file is not recommended. *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -p udp -m state --state NEW --dport 53 -j ACCEPT -A INPUT -p tcp -m state --state NEW --dport 53 -j ACCEPT -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT
5. Restart iptables
[[email protected] ~]# service iptables restart iptables: Flushing firewall rules:             [  OK  ] iptables: Setting chains to policy ACCEPT: filter      [  OK  ] iptables: Unloading modules:                [  OK  ] iptables: Applying firewall rules:             [  OK  ]
6. Test DNS configuration and zone files for any syntax errors
[[email protected] ~]# named-checkconf /etc/named.conf [[email protected] ~]# named-checkzone unixmen.local /var/named/forward.unixmen zone unixmen.local/IN: loaded serial 2011071001 OK [[email protected] ~]# named-checkzone unixmen.local /var/named/reverse.unixmen zone unixmen.local/IN: loaded serial 2011071001 OK
7. Test DNS Server
[[email protected] ~]# dig masterdns.unixmen.local ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> masterdns.unixmen.local ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49834 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1 ;; QUESTION SECTION: ;masterdns.unixmen.local.INA ;; ANSWER SECTION: masterdns.unixmen.local. 86400INA192.168.1.100 ;; AUTHORITY SECTION: unixmen.local.86400INNSsecondarydns.unixmen.local. unixmen.local.86400INNSmasterdns.unixmen.local. ;; ADDITIONAL SECTION: secondarydns.unixmen.local. 86400 INA192.168.1.101 ;; Query time: 6 msec ;; SERVER: 192.168.1.100#53(192.168.1.100) ;; WHEN: Thu Mar  7 13:07:56 2013 ;; MSG SIZE  rcvd: 114
[[email protected] ~]# nslookup unixmen.local Server:192.168.1.100 Address:192.168.1.100#53 Name:unixmen.local Address: 192.168.1.102 Name:unixmen.local Address: 192.168.1.100 Name:unixmen.local Address: 192.168.1.101
Now the Primary DNS server is ready to use.
Setup Secondary(Slave) DNS Server
[[email protected] ~]# yum install bind* -y
1. Configure Slave DNS Server
Open the main configuration file ‘/etc/named.conf’ and add the lines as shown below.
[[email protected] ~]# vi /etc/named.conf // // named.conf // // Provided by Red Hat bind package to configure the ISC BIND named(8) DNS // server as a caching only nameserver (as a localhost DNS resolver only). // // See /usr/share/doc/bind*/sample/ for example named configuration files. // options { listen-on port 53 { 127.0.0.1; 192.168.1.101; }; listen-on-v6 port 53 { ::1; }; directory "/var/named"; dump-file "/var/named/data/cache_dump.db";     statistics-file "/var/named/data/named_stats.txt";     memstatistics-file "/var/named/data/named_mem_stats.txt"; allow-query   { localhost; 192.168.1.0/24; }; recursion yes; dnssec-enable yes; dnssec-validation yes; dnssec-lookaside auto; /* Path to ISC DLV key */ bindkeys-file "/etc/named.iscdlv.key"; managed-keys-directory "/var/named/dynamic"; }; logging {     channel default_debug {         file "data/named.run";         severity dynamic;     }; }; zone "." IN { type hint; file "named.ca"; }; zone"unixmen.local" IN { type slave; file "slaves/unixmen.fwd"; masters { 192.168.1.100; }; }; zone"1.168.192.in-addr.arpa" IN { type slave; file "slaves/unixmen.rev"; masters { 192.168.1.100; }; }; include "/etc/named.rfc1912.zones"; include "/etc/named.root.key";
2. Start the DNS Service
[[email protected] ~]# service named start Generating /etc/rndc.key: Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â [ Â OK Â ] Starting named: Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â [ Â OK Â ] [[email protected] ~]# chkconfig named on
Now the forward and reverse zones are automatically replicated from Master DNS server to ‘/var/named/slaves/’ in Secondary DNS server.
[[email protected] ~]# ls /var/named/slaves/ unixmen.fwd  unixmen.rev
[[email protected] ~]# cat /var/named/slaves/unixmen.fwd $ORIGIN . $TTL 86400; 1 day unixmen.localIN SOAmasterdns.unixmen.local. root.unixmen.local. ( 2011071001 ; serial 3600    ; refresh (1 hour) 1800    ; retry (30 minutes) 604800   ; expire (1 week) 86400    ; minimum (1 day) ) NS masterdns.unixmen.local. NS secondarydns.unixmen.local. A192.168.1.100 A192.168.1.101 A192.168.1.102 $ORIGIN unixmen.local. clientA192.168.1.102 masterdnsA192.168.1.100 secondarydnsA192.168.1.101
[[email protected] ~]# cat /var/named/slaves/unixmen.rev $ORIGIN . $TTL 86400; 1 day 1.168.192.in-addr.arpaIN SOAmasterdns.unixmen.local. root.unixmen.local. ( 2011071001 ; serial 3600    ; refresh (1 hour) 1800    ; retry (30 minutes) 604800   ; expire (1 week) 86400    ; minimum (1 day) ) NS masterdns.unixmen.local. NS secondarydns.unixmen.local. PTRunixmen.local. $ORIGIN 1.168.192.in-addr.arpa. 100PTRmasterdns.unixmen.local. 101PTRsecondarydns.unixmen.local. 102PTRclient.unixmen.local. clientA192.168.1.102 masterdnsA192.168.1.100 secondarydnsA192.168.1.101
3. Add the DNS Server details to all systems
[[email protected] ~]# vi /etc/resolv.conf # Generated by NetworkManager search ostechnix.com nameserver 192.168.1.100 nameserver 192.168.1.101 nameserver 8.8.8.8
4. Test DNS Server
[[email protected] ~]# dig masterdns.unixmen.local ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> masterdns.unixmen.local ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 21487 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1 ;; QUESTION SECTION: ;masterdns.unixmen.local.INA ;; ANSWER SECTION: masterdns.unixmen.local. 86400INA192.168.1.100 ;; AUTHORITY SECTION: unixmen.local.86400INNSmasterdns.unixmen.local. unixmen.local.86400INNSsecondarydns.unixmen.local. ;; ADDITIONAL SECTION: secondarydns.unixmen.local. 86400 INA192.168.1.101 ;; Query time: 15 msec ;; SERVER: 192.168.1.100#53(192.168.1.100) ;; WHEN: Thu Mar  7 13:27:57 2013 ;; MSG SIZE  rcvd: 114
[[email protected] ~]# dig secondarydns.unixmen.local ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> secondarydns.unixmen.local ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20958 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1 ;; QUESTION SECTION: ;secondarydns.unixmen.local.INA ;; ANSWER SECTION: secondarydns.unixmen.local. 86400 INA192.168.1.101 ;; AUTHORITY SECTION: unixmen.local.86400INNSmasterdns.unixmen.local. unixmen.local.86400INNSsecondarydns.unixmen.local. ;; ADDITIONAL SECTION: masterdns.unixmen.local. 86400INA192.168.1.100 ;; Query time: 4 msec ;; SERVER: 192.168.1.100#53(192.168.1.100) ;; WHEN: Thu Mar  7 13:31:53 2013 ;; MSG SIZE  rcvd: 114
[[email protected] ~]# nslookup unixmen.local Server:192.168.1.100 Address:192.168.1.100#53 Name:unixmen.local Address: 192.168.1.101 Name:unixmen.local Address: 192.168.1.102 Name:unixmen.local Address: 192.168.1.100
Client Side Configuration
Add the DNS server details in ‘/etc/resolv.conf’ file in all client systems
[[email protected] unixmen]# vi /etc/resolv.conf # Generated by NetworkManager search unixmen.local nameserver 192.168.1.100 nameserver 192.168.1.101 nameserver 8.8.8.8
Test DNS Server
[[email protected] unixmen]# dig masterdns.unixmen.local ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>> masterdns.unixmen.local ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19496 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1 ;; QUESTION SECTION: ;masterdns.unixmen.local.INA ;; ANSWER SECTION: masterdns.unixmen.local. 86400INA192.168.1.100 ;; AUTHORITY SECTION: unixmen.local.86400INNSmasterdns.unixmen.local. unixmen.local.86400INNSsecondarydns.unixmen.local. ;; ADDITIONAL SECTION: secondarydns.unixmen.local. 86400 INA192.168.1.101 ;; Query time: 30 msec ;; SERVER: 192.168.1.100#53(192.168.1.100) ;; WHEN: Thu Mar  7 13:47:55 2013 ;; MSG SIZE  rcvd: 114
[[email protected] unixmen]# dig secondarydns.unixmen.local ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>> secondarydns.unixmen.local ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 14852 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1 ;; QUESTION SECTION: ;secondarydns.unixmen.local.INA ;; ANSWER SECTION: secondarydns.unixmen.local. 86400 INA192.168.1.101 ;; AUTHORITY SECTION: unixmen.local.86400INNSsecondarydns.unixmen.local. unixmen.local.86400INNSmasterdns.unixmen.local. ;; ADDITIONAL SECTION: masterdns.unixmen.local. 86400INA192.168.1.100 ;; Query time: 8 msec ;; SERVER: 192.168.1.100#53(192.168.1.100) ;; WHEN: Thu Mar  7 13:48:38 2013 ;; MSG SIZE  rcvd: 114
[[email protected] unixmen]# dig client.unixmen.local ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>> client.unixmen.local ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 14604 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2 ;; QUESTION SECTION: ;client.unixmen.local.INA ;; ANSWER SECTION: client.unixmen.local.86400INA192.168.1.102 ;; AUTHORITY SECTION: unixmen.local.86400INNSmasterdns.unixmen.local. unixmen.local.86400INNSsecondarydns.unixmen.local. ;; ADDITIONAL SECTION: masterdns.unixmen.local. 86400INA192.168.1.100 secondarydns.unixmen.local. 86400 INA192.168.1.101 ;; Query time: 5 msec ;; SERVER: 192.168.1.100#53(192.168.1.100) ;; WHEN: Thu Mar  7 13:49:11 2013 ;; MSG SIZE  rcvd: 137
[[email protected] unixmen]# nslookup unixmen.local Server:192.168.1.100 Address:192.168.1.100#53 Name:unixmen.local Address: 192.168.1.102 Name:unixmen.local Address: 192.168.1.100 Name:unixmen.local Address: 192.168.1.101
Now the primary and secondary DNS servers are ready.
If you want to setup DNS server on CentOS 7, check the following link.
If you want to setup DNS server on Ubuntu systems, check the following link.